I'm no expert, but it sounds reasonable to me.
McMillan calculator for his 1:58 800, gives "Sprint" workout paces of 28.0 to 30.8 sec for 200s, so he's even within the suggested pace guidelines.
2min rest is 4x the workbout duration, which is pretty typical for a Daniels rep-type workout.
20x200m is, what, 2.5miles? That seems perfectly reasonable to me too, well within the 3miles Daniels recommends limiting Rep workouts to.
So, not only does it seem within his abilities, it sounds like he didn't even exceed what the "experts" (McMillan & Daniels) would recommend for the workout.