Just to clear up a couple of points:
In the tire industry, there are standard machines which measure force variation. When you see an OEM specify a spec, that's what they are referring to.
Hunter uses the term RoadForce. That's because they are not using the same technique and it doesn't correlate to the industry standard machine. Put another way, when the tire manufacturer says a tire is a 15# tire, that doesn't mean the RoadForce is also 15#.
I wouldn't call what the OEM's specify for force variation as strict. (or tight!) Some are, but the vast majority are reasonable relative to what can be produced.
Yes, tire manufacturers have looser limits when it comes to aftermarket tires. But unless you're choosing a make/model tire that is being supplied to an OEM, there will be a whole range of values, not just high ones. Put another way, a non-OEM tire line will have zeros and some large values and everything in between.
The vehicles listed by the OP don't set off alarm bells with regard to Force Variation sensitivity.
What does strike me is that there are multiple vehicle and multiple tire manufacturers. I'm looking for a common denominator.
I am aware of a couple of interesting tidbits.
Tires can be mounted such that the assembly has an artificially high force variation. I've been able to reduce the value by 1/3 just by making sure there is enough mounting lube so the tire seats smoothly and evenly.
There is a really peculiar phenomenon, involving humans and their ability to sense vibrations. It seems we have a memory about what a vibration feels like and even when that vibration is eliminated, the irregularities in the road will make us think the vibration is still there. I became aware of this when I was chasing down vibration complaints and supplied a set of "Zero" tire/wheel assemblies and the customer claimed he could still feel the vibration. I've encountered that situation repeatedly. It's such a strange thing.