Indeed there are not studies linked to in the repository post.

Independend of that I'd read the advice more as the avoidance of useless time. Useless in the really useless sense of time where you can't read, think, talk or anything because you are busy looking for the next connection, switch trains, hurrying along and such. "daily reading hour" sounds like quite productive use of time but is only possible if there are longer stretches of uninterrupted commute.