Channel and spatial/binaural tracks I'd expect, but separated tracks for instruments/vocals is a lot more time consuming and the kind of thing that studios/producers/masterers would bluster at enough that I wouldn't expect it to come close to giving Apple the volume they'd likely want.
It absolutely could be done, I just think that Apple would want very good coverage and studios would be very slow to provide this format.
Apple need the labels either way. They can't just go creating new derived works without a license, and the artists and producers would far prefer to avoid the artifacts of something that is overly automated.
It's already become pretty common for studios and labels to make stems available (stems are full multi-track files that can be used with a DAW) to industry insiders and even the public sometimes. There's a community of remixers, samplers, even a small cottage industry of YouTubers who work with these regularly. It wouldn't take them more than a few minutes per track to annotate which channel is vocals.
Stems are usually lossless files and have an intended purpose for remixing.
Do you stop at instruments and vocals or are we talking 100+ tracks? It strikes me as nontrivial work for very limited purpose. Apple can turn your vocals down so now your exports have to include extra tracks? I don't think that's a good enough sell. The labels do care about this use case.
It absolutely could be done, I just think that Apple would want very good coverage and studios would be very slow to provide this format.