Flying wild- The same tactic has been used at the company ive operated at also.
Intrance - If what you told me is correct, I believe that is illegal. You cant finish an FDP and go straight back into another duty other than a ground-based duty.
For example, admin or positioning. You could argue DAA can be used but you cannot go back on an FDP if you are needed.
I suggest reporting that behaviour to your union or CAA authority.