the sheer volume of basic scraper and exploit scanner traffic that sites get is truly staggering in some cases.
Oh yes, absolutely. I've seen sites with millions of legitimate active users where we just dropped 98% of traffic because it's all malicious, either exploit scanners or just plain DDoS attempts. Going back to your earlier comment,
I might have the wrong impression, but “Bot” in average Joe’s vocabulary seems to imply this kind of astroturfing (often not actually a bot) or spambot type of bot, not any kind of non-human request like how Imperva are (correctly) using it.
On paper, any kind of automated traffic, be it DDoS, scanners, or automated content generation is bot activity. What is happening now though is that while consumptive bot activity is steady (because the field is already saturated), generative bot activity is skyrocketing. What it means for humans is that it turns media consumption from walking through an orchard and ignoring the rotten fruit to wading through a lake of shit and finding half-edible scraps. And I harbor no illusion that it wasn't bad before LLMs - even years ago I remember resetting the filters on my Reddit client and the feed getting inundated with ragebait, porn, and all sorts of low quality content. But when I had my filters they were effective, and that is becoming less so these days.