This is precisely what I have been doing a lot over the past 10 months or so. I find that if I hit a wall with drawing but I don’t want to stop (and feel bad about being terrible) then I go back to this exercise. I find that drawing page after page of straight lines and moving onto parallels and perps in prospective and then drawing ellipses inside them is something that improves my technique.
And yes I mean Scott Robertson! (woops…)