It is not common practice to pull all remaining collective while at the entrance to a flare at 50-80ft.
No collective application is required during the flare other than a minor application to prevent rotor overspeed due to increase induced flow (depending on MGW, rate of cyclic application, low-inertia rotors, etc).
Techniques in high-inertia rotor systems may apply a small amount of "initial" collective (anytime), or if flare is nose-high enough when intending to do a zero ground run landing then application of a small, initial collective application may assist to definitely not overrun the landing spot.
All remaining collective should be applied in the last 5-10 ft (aircraft size dependent) to cushion the landing.
It is not recommended to apply all remaining collective at greater than 30 ft (especially without crash-resistant fuel tanks). Definitely not at 50-80 ft.