Check Airman: For CAT IIIA I struggle to imagine how PF could effectively scan for outside reference and make the decision at 50 ft, and then come head down to verify FLARE mode engagement. Same for CAT II, actually. PM is head-down and thus FLARE is his responsibility to verify and then announce to PF to keep him in the loop.
We don't have a "No Flare" call.
It is not necessary for PF to scan inside either. (S)He should hear "50, Flare, 30,20,10 Roll Out"
If "Flare" is missing by the time (s)he hears 30 then it is (her) his decision to take over manually or GA.