This is the answer, & I should change my vote to PVB Tower.It’s fairly uncommon to use different abbreviations for different locations in the same DVC resort and association. For example AKV Jambo and AKV Kidani do not have their own abbreviations as far as I know. The only exception I can think of is BPK for the Big Pine Key VGF2 rooms. And given that we don’t refer to the longhouses and bungalows as PVBL and PVBB, I suspect most people would just say “I booked PVB in the tower” or “I booked a Poly tower room”.
In general people just use AKV. I’ve seen alot of people use AKV-J or AKV-K when talking about their trip.For example AKV Jambo and AKV Kidani do not have their own abbreviations as far as I know.