I agree with what you have stated smoke. But how else do you differentiate between JBP cultivars that display different characteristics? I bought some 'mikawa' seeds with the understanding that they had the genetic trait of shorter needles. And in fact they seem to. Compared to other unknown sourced JBP I started at the same time and have had the exact same growing conditions and care, the 'mikawa's have remarkably shorter needles. Maybe I just got lucky. The naming of plants with binomial nomenclature has been so muddied up with common names, and as you say regional names, it seems it would be a hundred year project to sort it all out.
I'm not saying we should. Unseperate them I mean. What I am saying is that given enough time, a plant indeginous to a specific area that has attributes favorable to that area will exhibit new charicteristics of its new surrounding over time. Thus ruining the effects that made it so desirable in the first place.
For instance the local nursery brings in elms from China. When they get here the bark is wonderful, exfoliating, with bright orange underneath, the bark is dark like glistening coal. After one season in our weather, the bark turns almost white or light grey, becomes very smooth like ficus bark, the internodes get larger and the leaves change dramatically. All the great look of a chinese elm has been lost in one season. It is now an American elm indiginous to China.
Here in the central valley, I can buy shimpaku on the coast that is so tight it looks like hinoki cypress foliage. Same with itogawa. After one season here the plants become almost unrecognizable as to their genetic makeup. This is in an unkempt condition. I mean under like circumstances as in a nursery in Monterey CA and Fresno CA.
The growing conditions of our differing climates makes a huge impact on how a plant looks as it grows. This is what I mean by comparing Mikawa pines grown in Mikawa Japan and anywhere USA. Climate has a huge impact on how plants grow.
Your conditions may vary! (edit: as I look at your region and see Toronto,Ontario Canada compared to Fresno CA, I can see why our perception may differ. Compared to a globe your much closer in conditions to this clmate than I am....significantly different.)
OK, carry on.