I think this has been discussed before, but here is a thought:
So - lets say my page height is 640.
I show a group that contains a “stretch to fit” (picture, text etc)
My page height then stretches to ex. 970
Then when I hide the group (that has been stretched); the effect is still there and my page is stuck at 970 height for a while. This is an issue when the UI is designed in the context of 640 height.
So my thought is this:
A default backend functions that says something like
"When a group that contains an element, with “stretch to fit” = yes - gets hidden > revert to original page height (variable)"
Not a huge issue; as there are likely some work arounds + few users suffering from the issue.