That was the part that stood out to me as well after watching The Verge's video: https://youtu.be/mpKKcqWnTus?t=98

The Vision Pro uses optical sensors for hand tracking, so if your hands aren't visible to the device it obviously can't track them. Electromyography solves that problem, and I could imagine Apple integrating some variant of this in a future Apple Watch, and just falling back to optical sensors if you don't own one.