"Warming down" allows the circulatory system to return to normal after exercise.
Cyclist who finish a hard ride and simply stop and don't 'Warm down' will encounter 'Blood pooling' in the legs.
This will lead to dizziness when standing up quickly from a seated or worse, a lying position.
My 'Warm down' consists of walking from the bike shed to the showers, approx 30 seconds. Then some stretches and light 'walking on the spot' while tepid shower water flows over me.
Stretches can be done with soap in hand.