There is nothing they can do, anything they can imagine to use as a signal for a bot user can be made to look legitimate. There is no way to win.

My college English professor was so obsessed with beating cliff notes that all of tests were hyper focused on the most obscure details he could dream up. It was just impossible to maintain a full course load and memorize what was the 1st, 3rd, 5th, 7th , last, etc word on every page and which character spoke it. Did the sentence contain any commas? How many times was the nurse mentioned in chapter X, etc.

Google can always follow his lead and make their data impossible to access, but impossible doesn’t increase ad views, so they will never do it. People using ytdlp is just the cost of doing business.