"It would've been cool if you could drag windows around so the minigame you're currently busy with didn't get obstructed by another window (but I suppose this was an intentional design choice)."
Yes exactly. People with disabilities don't necessarily get to choose the time and place where they will have to deal with their symptoms, so this specific design decision was in service of that. It simulates having overlapping symptoms, when the player is forced to take their attention from dealing with one symptom and instead engage with another with a totally different resolution method.