Clever.

I don't get why people can't just label their ads with random letters though?

because people have a job of building a website with a side of maintaining ads visible, while ad blockers write filter for a job all day long - in other words, it's a uphill battle, takes loads of time to test against all ad blockers and the effort can be nullified in few minutes of any adblocker dev time. heck, they can even crowdsource rules.

uBlock Origin isn't affected, apparently.