I think I just suffered brain trauma. You realise that he would have to be doing it constantly to stop her from gaining her full powers? Nothing you just claimed makes any sense whatsoever.
The phrase is something he can use any time to mentally control her, it's not the same thing. After the event Valkorion couldn't just suppress her again because she'd gained so much power in his absence.
Suppressing power is far more difficult than TP domination.