is it clear that they were doing it 3 times a day? I had in my head that this was for shaharis only, but now when I looked at it, this might indeed be for other tefilos also. Still, if they did mincha/maariv, I don’t think they meditated between them rather than listening to a Kitzur class!
For shaharis, this is not that remarkable – we are talking an hour before/after shmone esre (tefilah), not before pisukei zimra/shir shel yom or, for chabad, tehilim for rebbe’s age.
Also, given that they probably also worked, their daily calendar is not clear. Maybe they did not sleep much; started a shaah before sunrise, or it is really taking just an hour from the work day.
And – nobody said that shaah is an actual hour and not just a “significant amount of time”