I'm just guessing based on the issue with bots and spam on Nostr. I don't know for sure or if it's even possible to have accurate data one way or the other. My instinct is that we could estimate pretty well based on some metrics, but I don't know what they are. Definitely not my knowledge area.

I should say I'm sure many are, but I have no clue what percentage 'many' means. It could be a small number. But I suspect it's far easier to pump follow numbers using bots on Nostr than any other platform.