Stemmed from Issue 801294 comment#10, mccanny@:
After splitscreen is opened, closed, the divider moved or the device rotated, all of the windows in overview should have their sizes updated (assuming it's possible performance-wise).

The overview windows in splitscreen were intended to match the aspect ratio of the overview side of the split, not just when they snap. You can see that in the top video in go/splitscreen-motion. An early conversation I had with Omri made me think we were avoiding updating the ratios for performance reasons. Living with the feature for the last couple of months though, I think inconsistent window sizes in overview depending on how you got there is contributing to a feeling of unpredictability in the feature.