Premise: The maintenance the Soldier goes through just after he has been brought out of cryo is meant to reacclimatize him to being awake and active.
That it is the Handler that’s responsible for it is meant to give the Asset and the Handler a chance to renew their bond. Each Handler supposedly develops their own process but no one ever talks about it.
Turns out there was a good reason for it because those two hours before going on ‘active duty’ the Winter Soldier is far more alert than management knows and he insists on how he wants to spend it.
When Brock Rumlow chooses for his first action as the Soldier’s new Handler to lead him to the showers for a warm shower the Soldier takes advantage of the fact they are expected to ‘bond’, that Brock inexperience means he doesn’t know were the boundaries are and what's permissible, and that this is his one chance to establish a new pattern… a pattern he will enjoy.