I think it works like this :
in db
players have attributes like :
player.starhead = true or false.
player.starhead.texture = null or id of the file texture (111).
The texture files have attributes like:
head.id = 111
head.file = 1564.png
When a player already have a starhead but its updated via title update:
head.file value is changed or 1564.png is updated
no need to update squad file and since existing career saves are probably just and copy of squad file updated during your career:
player.starhead.texture still value 111, starhead will be updated.
lm pretty sure it works like this until this year.
the issue with this is when your player have player.starhead = false.
In this case, u used to need a squad update to change player.starhead to true and player.starhead.texture from null to id of the file texture (112).
So your already started career will not get the update.
BUT
maybe cranium faces have change everything, maybe cranium face are generated png and every player have starhead at true and a file texture related.
Maybe as textures files are not squad update related, textures will update just with title update ?