I'm not sure about the "learns about self-custody" part. I have friends who are like forever on Binance and still don't think about self-custody. They just enjoy the fiat price going up in their Binance app.
Discussion
I'll be honest, I started my bitcoin journey on Binance (was only about 3 months). A lot of people start on these platforms thinking they can "get rich quick" in crypto. Once the value of the coin is recognize over that of fiat is where the shift happens and then folks start to look at self custody. So for learning, sure there can be benefit. But no real bitcoiner is going to be on these trading platforms cause we know better.