I don’t think it’s absurd, especially when you consider that there may be times when he does do the mitzvah himself (for example, she’s in the hospital).
The reason the minhag does follow her is probably precisely because she is the one who physically performs the mitzvah, so it’s hard to find an example.
The closest I can think of off the top of my head is that if someone has a minhag to do metzitzah b’peh, he will hire a mihel who will do it, rather than rely ib the mohel following his own minhag.
It’s not a perfect example, though.