Commute time is useful, but it is also fragmented. I do not expect myself to fully learn a new concept for the first time while walking through a station or switching trains.
What commute time does well is repetition. If I already know a source matters and I already touched it once, audio helps me rebuild the structure without reopening the screen.
That is also why I care so much about mobile workflows. High-frequency learning does not only happen at a desk.