It’s not just “did you click the like button”. It’s “did you swipe it away? How long did you watch until you swiped it away? Did you come back afterwards? Did you let it loop multiple times before moving on?”.

They’ll capture likes and dislikes you yourself probably didn’t even knew you had, just from tens and hundreds of these micro actions. And they’ll do it in the very first hour of you using the app, whereas YouTube won’t know too much about you even after months of you using it.