maybe this is related to some other heuristic they're using for determining whether or not to show recaptcha (although this is in a no-extension Chrome on a residential IP address).
Right, they have that at registration but it's either superfluous or it only catches the really easy stuff because they rely on an army of human moderators who spend all day cleaning up after bad actors able to click buses.
In practice it is a major pain to keep up to date, and bots slip through all the time, at least on the subreddit I help moderate. It's a lot of manual volunteer work.
