Here’s a couple photos of the Number 1 Amazing Thing in my garden, Mongol’s Hat. It is ‘Nightmoss’ x "Fa’s Marbled Moss’ and where the heck it got the miniature gene from I cannot for the life of me imagine. It stays small and neat, suckers but the suckers are never more than a few centimeters away from the main plant, has a nice flower and a passable fragrance, but it’s these wonderful buds that really catch the eye. It doesn’t set hips; haven’t tried to use the pollen yet.
Very nice Fa. Love that it is miniature. If you need a test garden in the mid atlantic states keep me in mind. 
Fa, you bring up an interesting point “where the heck it got the miniature gene” which is a point I have been wondering. I am aware of the Rouletti derived miniatures which may or may not be the same as miniature chinensis, and with the mixed geneologies of modern roses, there is always a chance for miniaturism to be lurking. And then there are some species that are not humongus growers. But are there other pathways that lead to healthy, thriving miniaturism? And does this happen randomly? Anyone?
Ralph Moore theorized there were many roads to miniaturism. Wichurana has one. Why not others?
Gorgeous rose you have there Fa. Are the leaves scented like Nuits de Young?
I crossed Prairie Celebration x Pretty Lady a few years ago and ended up with some miniature types. I never really did run the numbers, but I would say that out of roughly 20 seedlings from the cross at least 3 are miniatures. They are very compact little mounds.
Miniature tends to dominate, too. Otherwise, how could so many minis have resulted from crosses with HTs, species and large shrubs?
Maybe I’m on the wrong track, but I make a distinction between miniature and dwarf. Dwarf is primarily short internode distances. Miniature is small parts all round. If you look at really small minis with multiple copies of the gene (s) all the parts are fairly in proportion. As you dilute it from tetra to trip, or dip everything gets bigger making patio roses or such. Kim is right that the miniaturization gene tends to dominate so we can have tetraploid minis with one or two copies of the gene(s). They do tend to be bigger though than something with 3 or 4 copies.
But a dwarf may be adapted to growing in a terrain where being close to the ground is a big advantage. As for instance in the alpine meadows or places where ruminants graze, or only snow cover protects from freeze damage. There are lots of dwarf conifers in which the needles are pretty much like the full sized forms but the stems are stubby.
I guess I mentioned this years ago in a newsletter. I tried growing out many OP seedlings of Circus. They made big flowers about the same size as the parent, but were runty dwarf bushes. Even a cross to Carefree Beauty which I kept, has full-sized leaves and flowers but never gets about about 1 ft high.
So is Mongol’s hat a dwarf? I’ve not seen a ruler on it, but kind of looks that way to me. Neat plant.
You know, I’ve been thinking about that, and I would be be prepared to say it’s a dwarf. It has hardly any internode distances, and it grows painfully slowly. It has 3 leaflet leaves almost exclusively, and is just a nice, tiny, compact little rose. Hopefully it will bloom today, but it even takes forever to do that.