Honestly it was so nice of the Galra to let Shiro maintain his undercut, like if you’re not gonna let a guy keep all his limbs you at least gotta let him keep his aesthetic damn
That’s actually a tactic used on POWs in the past.
They’d groom or wash their captives to instill, further, that they are helpless and a possession, or a pet, and not a human being capable of washing themselves. It also ruins their pride and makes them feel violated, or childish, to be unable to control their own grooming.
In some situations it’s used as part of a brainwashing move. If the prisoner is complient and obeys, they get rewarded with better food, grooming, and sleep. It’s to further control over the prisoner by using the most effective teaching technique, positive reinforcement.
So they may have kept Shiro groomed in a sense, to further show he’s 1. under THEIR control, 2. a possession, and 3. a reward for doing as told.
IT GOT BETTER AND THEN WORSE