If you’re giving those companies personal info (name, phone, address, CC) they can track you regardless of what emails you use with each of them.

Good thing I’m not doing that.

And if you’re not giving them personal info I don’t see how that works.

…how what works, exactly?

Yeah so I register on both random site A and random site B with aliases @tfyuhegddssgvd.com, so what? How are they going to find out about each other?

You ever look at the Privacy Policy on any website ever? They all sell your information to data brokers.

And why risk a GDPR violation for such silly reasons?

It’s not a GDPR violation. And even if it was, that only applies inside the EU.