@mariachan A lot of it is going to be based on your settings and all. For example, what’s your Shield settings when visiting YouTube? If you allow Fingerprinting, then that’s allowing them some bits of tracking for you. The other thing is to realize that Brave only stops ads and some trackers, but that doesn’t prevent your internet provider from sharing your information. If you don’t have your IP Address blocked by running through something like a good VPN that doesn’t have any leakage, then they will be able to identify you and serve things based on your area.
To get to what I mean about VPN with no leaks and all, check out this topic I’m linking below. While it is exact to your situation, it is lightly related in terms of what data gets shared with sites and all.
And again, if you aren’t blocking cookies and fingerprinting, then they might be plugging in temporary cookies or other identifiers (they can track in other ways outside of cookies) to have your watch history.
I’d advise to check out https://brave.com/privacy-updates/4-fingerprinting-defenses-2.0/
Or for a little more detail, you also have https://blokt.com/guides/browser-fingerprinting
There’s honestly a LOT of moving parts when it comes to privacy and tracking. Brave does its best to help prevent cookies and fingerprinting, but they are far from being able to completely stop it. Hopefully the resources I provided in the other post I linked to as well as the websites I just linked here, you’ll be able to get some of your answers.