Came across this recently too, seems to be from "Amazon Quick" where crawling other's websites is basically a feature of the product: https://docs.aws.amazon.com/quick/latest/userguide/web-crawl...

> Crawling behavior [...] Crawler identification: Identifies itself with user-agent string "aws-quick-on-behalf-of-<UUID>" in request headers.

Maybe people found a way of using it as a loophole for something or Amazon Quick is just picking up in usage, and your website is popular amongst whoever uses that sort of stuff.