You make a really good point about 35x12.5 not being the only tire option that one should consider. However, when I checked out the selection of 35" tires on the Stage 3 website, you also said this: "Any truck that's being built for rugged off-road use or a truck that just needs a much more aggressive look should have a set of 35" tires." Thoughts?
Considering that you can buy a 35" tire for a Raptor, Super Dutys (and you only need a 2" level to clear them on most F250s and F350s), other 3/4 ton trucks, Jeeps, and anything else there's nothing really inconsistent here. In the case of the F150s, 35x12.50" tires are generally more trouble than they're worth, though they're still an excellent option if you're willing to trim, spend a lot on a lift and wheels, or just don't care about rub in the first place.