One thing they said early on in the ~2 hour video I was watching was that, while AlphaStar had access to the full data of everything within its fog of war, it seemed to need to partition its access to it, in a way that was similar to a human checking different screens, and did so about ~30 (or was it 37?) times per minute.

This might be why changing to having to observe only one screenful at a time (rather than the zoomed out view) didn't seem to have as large an effect.