As someone who has messed around with said flags, they probably never will be.Yes. They are a little too unstable for general use at the moment.
If a non Corrin unit has the flag, a lot of stuff breaks.
A) If Corrin stops existing and this unit becomes player, the game crashes.
B) If Corrin never exists, but this unit spawns, the game crashes.
C) Any save where this unit supersedes Corrin will become unuseable. The game will work just fine with both Corrin and this unit, but the moment you save and quit the save will no longer be usable when you try to load it unless you get rid of the offending unit.
D) Even if you somehow make it past all the crashes and the game breaking itself, in some instances the game will try to use a Default Male Corrin in cutscenes and a lot of stuff will crash with this Corrin.
That's just off the top of my head.