I have hundreds, if not thousands of Meshes and Animations in countless projects (and I doubt I’m the only one). If these projects are updated to 4.16 and you want to add some new stuff to the existing skeletons or just reimport an existing asset you will get all kind of fancy errors, bugged animations and state machines thrown in your face.
If you’re going to change the import hierarchy in such a drastic way I’d expect it to be optional and not a statement like “well for the past 3 years things were imported that way, but now you can redo everything as your rig is bad, bro”