Users coming from other software expect Quad View to behave a certain way. Since rBd71db08f6d31, when exiting Quad View we always toggle to the User Perspective (top right) view, rather than the one the mouse currently hovers. That differs from what users probably expect (see T43523, T42462, T42368, T43452, T69717).
It should not be hard to get the (presumably) expected behavior to work again while addressing the reasons it was removed.
- Maximize the hovered view when exiting Quad View
- Keep rotation of that view locked if it wasn't the User Perspective one
- Keep the view transform of the User Perspective stored so when going back to Quad View, it shows that in the top right.
For more details, see rBd71db08f6d31.