Religious Tolerance: Possible Religion Bug?

I have noticed that when a Catholic governor with any piety points is in a settlement with 100% Catholics, each point of piety adds 5% unrest to the settlement. I thought it was supposed to be the other way round, could anyone confirm if this is a feature or possible bug?

I noted that on the buglist a while ago although with a different explanation:
For me it was only in capital cities where having any governor would cause 10% religious unrest regardless of whether he had piety or not and how much piety he had.