Being a new truck pretty much anyone with minimal mechanical background would find that leak and a bad wheel bearing. If it's just the gasket then why is the dealer not replacing it? The only way to tell with certainty is to clean off the effected area, start the motor and see the root cause of the leak. I recommend baby powder before going with the dye. Did the dealer even diagnose exactly where it was coming from?
You are giving people far too much credit. The bearing wasn't howling, it was ever so slightly weeping, your average Jim or Jane Q. Public isn't climbing under their brand new vehicle unless there is something obvious going on and your average Lube Tech isn't going to spot either of those things would be my bet.
Regarding the gasket, they do not sell it separately, the cooler is sold as an assembly, as the OP has noted later in the thread. He cleaned it off with brake kleen a few times and couldn't ascertain where it was coming from as the amount is exceedingly small. Reminds me a bit of my FRAM Ultra saga where they were unable to reproduce the gasket weep I experienced. A replacement filter didn't leak however, so clearly the filter was at fault.
These kind of issues are unacceptable on a new vehicle. I feel bad for "The Critic". I'm sure he is not happy at all having to deal with this. At this point I would recommend documenting every visit and have the vehicle replaced under the lemon law.
No OEM on the planet is going to lemon law a vehicle because it has a clearly defective part that can be easily replaced and solve the issue. The lemon law is for vehicles perpetually in the shop, typically for electrical issues that are never properly resolved.
IMO, the dealer is not doing the right thing by sending the vehicle away with a leak and only one hub bearing replacement. Hub bearings are always replaced in pairs when doing a legitimate customer repair. Even with low supply there are plenty of new 5.7 Hemi vehicles on the dealers lot and assembly line to R&R a part in order to fix one that is already on the road.
As the OP noted and several others, no, bearings are not replaced in pairs, and FCA wouldn't have covered the replacement of a clearly non-defective hub on the other side. I also don't think somebody buying one of those trucks that's already had its bearing poached would be overly pleased in finding that out, which is why that practice is likely exceedingly rare and not endorsed by the OEM's.
Our Tahoe had one leaking Sachs shock and they replaced the pair under warranty.
It makes sense to do shocks in pairs (even if the OEM won't cover it) because their damping characteristics change over time. A wheel bearing can easily last the life of the vehicle and its performance will remain unchanged for that entire period.