while not ad related, interesting
lot of theories going around about them training ai for the last month or so. apparently if the ai thinks you are kid, based on viewing habits, it will turn on restricted mode. another theory, if not seeing channels that you watch new content as it is released, the algorithm only thinks you like a channel if you watch 2-3 vids in a row.
i know they did something as every time they fiddle with the algorithm, i start getting recommended vids that are 10-15 years old.