Point one: I’m pretty certain they already track that. With or without account. And you’re on the internet, without a VPN there is no privacy. You are also able to remove that history any moment you want.

I mean sure, they could try combining the user agents my unofficial apps provide with my carrier’s NAT IP to build a profile on me, but it would be highly inefficient and imprecise to the point where it’s almost useless for them. With a Youtube Premium account they have an identity tied to an email address, full name, and payment info that they can relate every click in their apps and websites to. If I also use their other services with the same account, I would be paying them to spy on everything I do and sell my data, so other companies can sell me crap.