Not to Mozilla, but to whichever DoH service Firefox is configured to use, by default or by the user. Mozilla isn't running a DoH service.

To be fair, can anyone really expect otherwise?

If you insist on using a third party resolver for name resolution they will have knowledge of your queries no matter what the protocol. Doing it over tcp and http is not any better, or worse, than doing it over udp. This is something you have to opt in to.