Several topics are actually embedded in your question ...
First - what about warranty? Warranty of the vehicle, and warranty of the filter product.
If you are under warranty for the vehicle, then it's advisable to follow those guides using products that meet the specific product fitment. I do not mean to say you must by the OEM brand, but you do need to follow the OEM requirements (not the same as recommendations BTW). Since these are not often published for we consumers, we rely on the aftermarket to fill this void for us. Using a Fram/Purolator/Wix/Baldwin/Etc is OK as long as you use something that they also require. Often, actually almost always, the warranty of the vehicle and product is predicated on following their guides. If your vehicle is not under warranty, this part can be ignored. But you also have to think about the filter warranty; read on.
Understanding warranty is about realizing where the burden of proof lays. It's not that you cannot use a product outside the requirements of the OEM or filter maker, but when you do so, they have the plausible position to at least delay any coverage, if not outright deny it. When you use their products as prescribed, should something go wrong, it is upon them to prove that you made a mistake. If you go out on your own, they can (at a minimum) delay/deny coverage until you can prove (in court or arbitration) that your decision did not cause the doom that may have happened. In this case, it's you against Goliath. They have mounds of data, lots of lawyers, and time is on their side. You have a bunch of BITOG know-it-alls that won't show up in court, and most cannot articulately describe why they think "bigger is better", etc.
Next, after warranty, comes the understanding of the variation of applications from OEM perspective. I will never understand why there are not perhaps only 25 filters for nearly any engine in the entire marketplace for any given industry. As you see, there are common mounting options, similar sizing, similar pressure ratings, etc. For example if a FL910 is OK to use on a Fusion 2.5L and a FL400 is OK on a Taurus Vulcan 3.0L, why cannot they interchange officially? Beats me. I've seen probably more UOAs than anyone here, and I have yet to see any correlation between filter size and wear rates even when OCIs are 2x or 3x the OEM limit. So if the smaller filter (FL910) is OK for 7.5k miles on a Fusion, they why not a Taurus? Am I supposed to believe that extra 500cc of displacement warrants a bigger filter? To some degree, it's just crazy. I do completely understand why there are different packaging choices and constraints, but I would think that if the industry got together and made a concerted investment in logic, they'd find about 25 different filters that would succeed in probably 95% of ALL applications. Yet there are literally hundreds of different filters out there just for cars alone.
After that comes the topic of "close enough is good enough" when viewed from the aftermarket. There are plenty of examples where perhaps the target filter is a high-volume seller (say FL400). You have already noticed that Fram, Wix, Puro, Bosch, Baldwin, etc all make filters that are not EXACTLY the same size/pressure/bypass/etc, but they all will warrant their own product for that specific application. They realize that "close enough is good enough". The engine really does not care if the filter is an extra .200" taller, or .125" narrower, or has a bypass lift-off at 9psi, or 10psi, or 11psi. It needs to work at it's main job; filtering chunks from the flow. Past that, as long as it fits and the parameters (size, pressure, relief) are near the OEM spec, it'll work just fine. The irony is that when they do it, they will back it up with warranty, but if YOU do it, you're on your own.
Common sense says that anywhere an FL400 can fit, without danger of physical damage, an FL910 should hold up fine. And vice-versa. But woe unto those who ever have a problem should the unthinkable happen.
I actually do this at times; I use filters that are not "approved" for the application. But I only do so with equipment I can afford the risk, and am willing to experience downtime, and ultimately risk an uncompensated loss. And I vet my choice with nano-precision. I double check all factors. While I am willing to do this, it is rare that I do so.
The key is to make 100% (total absolute) assurance that you didn't overlook some important thing. An excellent example is a guy I read about on another forum that wanted to use a GM filter from one application for another. He nearly did it, until I pointed out that the filter he was wanting to use didn't have a bypass valve in it, although the application did. GM used to put the bypass valve in the block (as did some other OEMs at times) and so the filter didn't have a BP inside of it. But the application he was fitting had no such valve in the block, and mandated a BP in the filter. He risked serious damage should either the filter blow apart the media, or etc ... All because he noticed that the gasket size and threads were the "same". So the caution here is to be 100% sure you've looked at ALL APPLICABLE CONCERNS prior to substituting a filter outside of the recommended application. I am not saying you're dumb enough to make this mistake, but by gosh, we all know someone that is, right? The internet is now full of videos of folks that thought they knew better ... It's funny when it's not your car/truck/tractor/tire/house/mailbox/hands/eyes/wife/daughter that is, at a minimum, inconvenienced or worse, hurt.
Two examples make this clear:
Scenario A
You're at home, stuck in a raging blizzard for three days, your electricity went out 12 hours ago, and how you have no choice but to run the generator or risk your son's breathing machine running out of battery back-up power. You NEED this engine to run right NOW, and the filter on it has burst through a rust spot. You have a "darn close enough" filter in the garage. It fits, but it's not "approved" for the generator. Your nearest auto-parts place is 2 hours away driving in 12" of snow. In this case, by all means, save a life and put that "wrong" filter onto the generator. Do whatever it takes. As long as the specs are "close enough" it's going to save your life, save a home from burst pipes, save a barn full of animals from dying, then OK, do it!
Scenario B
You just put $5k into a motor rebuild, on a labor of love hot-rod project, and you think "Meh ... this filter might work", and the risk is blowing a motor that is not a necessity to run in the next 20 minutes, then that's just plain silly to me. Can you not get a filter tomorrow on the way home, or have the spouse pick one up at W/M while getting groceries? How important is it to hear this motor run immediately?
Risk v. Rewards!
