That's an excellent observation and question, Jill.
I took about 50 cuttings in Oct./Nov., and most of those were rooted over the fall and winter.
Those and seedlings are what's now available. Because all my mature plants, anywhere from 2 yr. to 20+ yr old ones, were dormant during the fall and winter months, they are basically leafless and have few viable roots. That's just their nature. About half were left in their pots, but remained dry and leafless and half were without soil and were bagged. I had a handful that over-wintered in the solarium, some in bloom in the fall and those that had seed-pods. Those all finally did go dormant in late winter and lost all or most of their leaves. I am actually still in the process of potting up all those bagged plants, so basically, the majority of my older plumeria are still in dormant-mode. I really won't even begin to take cuttings until they have substantial growth and that's not going to be until June at the earliest. I will be able to take a few cuttings from those that over-wintered in the solarium simply because I did not cut them back in the fall. But even with those, I won't take cuttings until that have begun to leaf-out. I want the cuttings to be nice and strong and that just takes time.
That's the problem living in a temperate region of the country. I have to allow for dormancy. Those in the far southern regions of the country, in the sub-tropical zone, have an advantage over me. Their plants will go semi-dormant and thus, their time of "non-cutting" is shorter than mine.
If you like, I will take a look at those few plumeria that came out of the solarium and see if any cuttings can be had.