i disagree... i have had coaches who did not get as far as their students... could not do the things their students eventually accomplished, and they were good coaches... and come on, the Suzuki method has been around a long time... my sons have had a wonderful piano teacher who has taken them further than she has gone personally...
I think you misunderstand me, I actually agree with you.
Good coaches teach their students to be better than them. They’re able to do so often at least partly because what they’re doing doesn’t come naturally, so they have to figure out the details.