hmmm, not sure I have an answer to that - possibly both - but it is accepted horticulture practice with all kinds of succulent and semi-succulent plants (such as plumeria) that cuttings should callous before attempting to root them.
I have definitely observed that a well calloused cutting will root very quickly and hardly ever develops rot.

Perhaps you have a scientific basis for the time a "callous" forms, Hetty. My comments only relate to my own experience and I seem to have the same result whether the cutting "rests" for 24 hours or for several days. As long as that cut-end is hard and dry, I pot it. The only cuttings I have ever rooted that were more than 3-5 days old were those that I either had to cut to overwinter a very large plant, or branches that got knocked off when I was preparing my plumeria to bag them for winter.

Mike, Hetty is far more experienced than I when it comes to plumeria and I would follow her recommendations.

Ken

I've enclosed a photo of the cut end of one of my new cuttings. Good enough to pot?

And the other end.

I think I'm going to perform a little experiment. I'll pot this one today, and leave the others to dryout another week or so and see which one's perform best.

A quick question about the leaves still on the tip; should I remove them and if so, how? Or, are they fine to leave?

You can leave the leaf-ends on - they will fall off in a few days by themselves.
I like the idea of doing a side-by-side study. Keep us posted on the results.

A man after my own heart. I am always experimenting with my plants. I have so many tropical plants that if I lose a few, I don't even miss them. I just completed shipping canna and ginger to 15 lucky people. All I asked for was the postage. The total weight of those 15 boxes - almost 40 lbs!

I wish I could have gotten in on some of those. I hear those gingers have a really great scent!

All you had to do was ask. The 'White Butterfly' Ginger does have a wonderful fragrance. Hummingbirds love them and now I am starting to see Luna Moths coming to them after dark. The moths are really early this year. Normally they show up about the time the hummers are going south, early October. I wonder if that foretells of some weather change a-coming?