Oddly, the instructor made the opposite argument, which sold us: He said that he found that kids that learned too early played by rote, and it was the kids that waited a couple of years (5-6yo) that could play piano as an art. At any rate, I think we are both looking for the same outcome.
I took piano lessons for about 10 years as a child. The first five I spent watching my teacher's hands and copying her, rather than reading the music which she thought I was doing. Eventually she caught on, and only then did I start learning the ability to play anything on my own. The first five years were by no means wasted--I learned a lot of physical technique--but I definitely didn't get as much out of those 10 years as I would have liked. Although, I started at age 8, so maybe I was just a difficult child. :P
He said that he found that kids that learned too early played by rote
-Somewhat harder to play by "rote" when you aren't reading but are relying on your ear. Still definitely possible, just less likely imo. Check out the Suzuki Method, I've been impressed by the people I've met that were thus trained.
I'm aware of it. This instructor said he is trained in the Suzuki method, and uses it. His point was that with very young kids, they need to look at their fingers when playing the piano, whereas they don't need to a couple of years later. He found that they needed to unlearn that behavior if they wanted to play freely and artistically. Maybe it's different for violin, which I think might make some sense.