Stephe and Lexy711, yes, there is an influence when resorting to FFS before HRT has done its work. The fat AROUND the areas to be changed is the problem. That, and the muscles in the face that do change. They attach to bones, and if they change after the bones have been altered, it can yield unexpected results in time. And in some cases, just fat movement changes the way we see the same nose or chin entirely. It's still big, but it doesn't appear manly anymore.
And yes, HRT can actually do something for noses and even chins. A large part of the nose is cartillage, which can be affected (though definitely not as much as skin or fat) by HRT. On the chin, there is also a little layer of fat/thick skin that can be reconfigured, possibly rendering less visible any butt-chin effect; the muscles of the jaw nearby, too, can change. Anecdotal evidence of subjects under 25 have also (unscientifically) seen reports of bone changes.
Plus, I think most people getting their nose and chin worked on will probably have other bits to do.
For all these reasons and even more, probably, I still think that in every case, the more you wait, the better it is. And even if you're right, I think that whilst whether or not it is harmful not to wait is discutable, everyone agrees that waiting can in no way hurt, right?