If a pilot does not flare at 10’ there isn’t really time to say I have control, you just need to take control. With a conventional yoke system, a Trainer or Captain could apply back pressure on their yoke which would save the landing and give feedback to the trainee, (followed by a debrief).
The Airbus FBW side-sticks do not move to mirror each other’s inputs - (I think they should) - so instead there is an algebraic addition of deflections. This means that in a no flare situation, the Trainer/Captain could quickly pull back and save the aircraft, but it is not correct for both pilots to be operating the controls, hence the “dual input” warning if the take-over button is not also pressed.
Airbus FBW nosewheel steering is also additive, and I once saved a Captain who suddenly veered over (for some reason) while taxying, and I grabbed my tiller and saved any embarrassment. There wasn’t time to alert him or say I have control.