Yes, they can observe my queries to authoritative servers. But I didn't claim that running your own recursive DNS guaranteed privacy; I only claimed that it dispelled all problems arising from relying on someone else's DNS recursors.

I happen to trust my ISP, BTW; I really just like running my own because I can observe what it's doing.

So your “alternative” is strictly worse / solving a different problem.

I can't "prove" it. But my ISP is a nerd ISP; it's Andrews & Arnold, a rather unusual outfit. If they were caught selling us out, they'd lose all their customers in a flash.