It shouldn't make much of a difference from the plant's perspective. It will bloom exactly as it was 'programed' to bloom -- like it's mother plant.

I suspect that growers who are adept at grafting (FC, for example) find that it's simply more cost-effective. Likely the plants take off much sooner than waiting around for 4-6 weeks for a cutting that may or may not root. I don't know.

I don't have a problem with grafted plants at all.

Grafting is very popular for those cultivars that are difficult to root. Or as Dave states for those who don`t want to wait on the plant to root.

Grafting plumeria, as other plants, has pros and cons, you can get mismatched grafts which restrict the growth of the tree, the graft takes over-this is fairly common in fruit trees, graft failure and other problems.

I have a friend who grafts about everything, I think he just likes grafting. I only have one grafted plumeria but no objection to them. I have several grafted citrus that do fine.
Tally HO!

Grafting is recommended for hard-to-root varieties, and those prone to black tip. The strong root stock of seedlings helps fussier plants to establish quickly and avoid some of the problems of a weaker root system.

OR..... your beloved grafted plant could get blown over on a windy rainy day and get broken right at the graft site leaving you to scramble looking for just the right tape that may hold it together and maybe heal and when you can't find that right tape inside the house then you have to rush outside to the shop in the pouring rain getting soak and wet only to realize that the break wasn't very clean and you probably should just go ahead and cut it completely off and start it as a cutting.

But you don't have the heart just yet.

I think its the expediency of grafting that makes it attractive to the sellers. I would assume that putting a cutting on top of an established root ball is like going from an old carburator to fuel injection on your engine.