What
The fullscreen mode exit survey prompt has been simplified. The old prompt included the parenthetical "(optional, Enter to skip)"; the new prompt is more direct.
Evidence
String change (old: "To help us make fullscreen mode better, what made you switch back? (optional, Enter to skip)" → new: "To help us make fullscreen mode better, what made you switch back?")
Strings lifted out of the shipped bundle, so the claim above can be checked against them.