It does, to a degree. With air-air heat pumps you get warm air and the air has to warm up the walls, furniture, ground and so on. Warmer air rises so in order

It does, to a degree. With air-air heat pumps you get warm air and the air has to warm up the walls, furniture, ground and so on. Warmer air rises so in order to warm up the ground (or your feet) it has to displace/heat all of the cold air first. If you vent before the room itself has been warmed up, you have to start over. Floor heating on the other hand heats up the floor and anything standing on it first. The heat still rises but by the time the hot air has displaced/heated all of the cold air, everything else will already be warmed up and give off heat if the air is vented. Of course the correct answer is that heat pumps don't need to be turned off because it's actually more energy efficient to run them at lower settings for longer. And with proper insulation heat loss from air currents is less of a problem so this is more of a consideration for heating up a room from scratch (e.g. after turning down the heat pump during a vacation).