How does sharing or not sharing widgets with blender make this “another graphics app reinventing the wheel”? Godot is a game engine, not [just] a graphics app.
But yes, Godot 4 directly translates interfaces with .blend files.
> dogfooding of implementing the UI with the engine itself
It's been pretty common in the past for every pro graphics app to build its own x-platform GUI widgets library. Was hoping this could come to an end, as it is a waste of time.