The proficiency bonus is just a static modifier that skills take their values off of, like any of your ability scores. I've done exactly the same thing when making both classes and subclasses, if you want a static modifier that grows with your character, isn't excessive and isn't tied to an ability score (and therefore currently immune to magic item trickery) its an option you have.
Not to dismiss your concerns, but if class power creep is your issue, then they also shouldn't add any of the subclasses from Xans either.
Last edited by Piff; 17/11/20 11:43 PM.
