When someone is a PhD, and you know this, and you choose to use ms/mr/mrs instead of dr (or omitting an honorific altogether, the most common, unobjectionable choice), it can easily be interpreted as condescension.
Dude, PhDs give a fuck about PhDs. At least in the States. I would find it odd to be addresses this way. When I addressed my phd supervisor the first time with professor doctor XYZ, he just said, I am Bill. My name is Bill!
Also like the one time you most typically use the Dr honorific is specifically when you are speaking about the person in reference to their profession.