Will position synchronization work if position has negative FTE

C is a parent position of B and B is parent position of A. C is having 4 incumbents and having manager who is on position A as position B is vacant.

After adding incumbent on B also they are having manager of position A. Even after running Position Sync process also manager is not updated. While trying some workarounds, we found that position C is in negative FTE. We ran Position Sync process after updating FTE of position C to positive value and then manager is updated to all the incumbents on position C.

I want to know is this expected behavior? Any inputs will be very helpful.