Have you tried it? Not a great experience. Apps don't get access to the camera feed so they can't actually detect your keyboard, you have to do a manual registration process which is janky. But the bigger problem is the quality of the passthrough. Depth perception and latency are especially problematic for this application. Cool demo but not worth using in practice. Maybe it could be better on Vision Pro.
Well, the point was the suggested software already exists, not that it would get the approval of everybody.
I agree that formal training and teaching with a quality provider is likely to be optimal but any tool that adds to the available options for training is worth exploring, especially if somebody already has access to the platform the software is available for - paid instruction is not always an option for many.
We also need to be careful not to gatekeep music by demanding instrument players go a formal route of instruction.