I do wish I read more, but I don't need to be repeatedly told "if you have time for [easy meaningless activity], you have time for [strenuous meaningful activity]" by someone that is not obliged to have strenuous, comparatively inflexible work as part of their daily life. Like sure, I have the time, but do I have the energy? Not really, at least none that can be inspired by telling me I'm being lazy for wanting to switch off for a bit.
Doing an undergraduate degree isn't easy, but if all you have to do is 10 contact hours a week plus 10 hours of independent (flexible) study, and you are funded by your parents, it's just different to having 40 set hours obligatorily blocked out by work. Grace has never had a normal job whilst financially independent so I'm not sure why she thinks it's appropriate to present her advice as generally applicable.