I dont know if I would generalise so much about these exercises. It depends a lot on the person what squat is appropriate for their needs. If you're trying to become more athletic, i think FS def has a place, but in my experience, you can't really make it your main squat. It beats up the knees and tendons pretty good. Guys like Pendlay have said the same thing, we've tried doing a FS heavy training cycle with BS minimally as assistance and it doesn't work as well as mainly BS with FS as assistance.
More conventionally, you can do a good amount of volume with BS and work up to a FS max regularly without any problems, as I've experienced. BS does a great job of driving up FS this way. I'm not sure if the opposite is true, it's not so easy to convert FS gains to BS, at least ive never observed that to happen. Also it's not easy to drive up FS either, progress isn't smooth like BS. With BS I could add 15kg to my squat and see an immediate 7.5kg increase in my FS. It's pretty hard to add that kind of weight to a stuck FS though as I had found being stuck for months on 3x129 and 1x136 before my BS pushed my FS PR up to 1x145 and i was probably good for more, but my main focus at the time was BS not FS so i didn't max out.
I dont know, i feel like if i only did BS i would get nothing athletically out of it. There are millions of people out there doing only backsquats who never see anything good happen outside the gym. I dont want to become one of them, so i keep FS in, just in case, it will help, at least i think it has helped me a little, how much, i dont know. I do know that as my BS climbs up, my FS goes up too, as long as I keep doing the odd FS here and there.
Btw the whole issue about hamstrings is pointless to me. I dont do any hamstring work and my thighs are mainly hamstring, they'll always get a lot of work when i squat, it's just how i'm built, i'm ok with it. Going to FS doesn't magically made it a quad/glute exercise, if anything, BS is a better overall leg exercise for me. I really dont know what FS does for me that BS doesn't.