LMFAO. Brave uses uBO's lists and filters, including trusted filters which have much more capabilities with much more risks to your sites' data and they allow that on all other lists too (even uBO only allows their own lists as trusted by default, other lists need to have permissions from users manually). That's how they can block youtube ads, and no they don't code their own filters for youtube ads either. And be assure that they can't check 100% all commits from uBO and other lists either.

If you want to play "no trust to a 3rd party dev", you should not use Brave's adblocker either. Or at least turn off all the lists inside it, and use your own lists. Your security risk is in those stock lists.