I rely enjoy mornings that come with an aha moment. I've been doing my own setups for years and found that I can get the strings very low but then can't get my finger to catch the string for the bend. So then I raise the strings a bit until I can bend easily. Then of course I have to push down a bit further for clean fretting. Yes I have vintage frets on several guitars and your explanation makes perfect sense. Why didn't you tell me this years ago?I think playing style and string gauge have a lot to do with that. For example I bought an American Original 50's Tele a couple of years ago which has the vintage size frets (~.040 high) and a 9.5" radius. With 10-46 strings and the vintage frets it was super tough to bend strings. The difficulty is getting your finger under the strings to bend it because the fret is not high enough. So I dropped the tuning down a 1/2 step to make bending easier which helped somewhat. I recently got that guitar refretted with Jescar stainless 6100 size frets and now it is a rock and roll machine.
With taller frets there is less contact between your fingers and the fretboard. This means you can apply less pressure with your finger for the note to ring out. This in turn makes bending, pull-offs and tapping easier.
I do wonder what magic Clapton used to do those bends on his Strat with those skinny frets.