I have a couple also that didn't have any leaf loss...

Lucky you to live where your plumies can grow all year.

Mark, I believe that one reason those leaves have stayed is because the vast majority of those leaves are relatively newly formed, right at the terminal of the tips.

I have a NOID orange that keeps most of it's leaves through winter. However, it doesn't grow new ones either. It is stuck in Winter's Suspended Animation. Once the new leaves start emerging, the old leaves from the year before fall off. I bought this tree as a 12" cutting in Corpus Christi, Texas where mostly plumeria don't go dormant. Maybe that's why??