I don’t have a problem with the clarity of ‘mutable’. Perhaps the confusion comes from the word ‘mute’ that can mean a ‘reduction of strength or intensity’. So it is a misunderstanding to associate the term ‘mutable‘ with the word ‘mute’. in this case ‘mutable’ does not mean ‘able to be muted’.
I would suggest to continue referring to the ports as mutable, even if there is a misplaced ambiguity.