Answer: I think many gardeners use the name "Japanese Cherry" to distinguish the trees grown ornamentally for their flowers alone from the sweet and sour cherry trees grown in orchards for their fruit.
Orchard trees are sometimes grown on, or grafted onto, dwarfing rootstock. This results in a "dwarf" tree that stays smaller than it normally would in terms of height and width (this makes it easier to harvest the fruit) but does not affect the trunk size or fruit size.
Also, to make it a little more complicated, specific varieties of a tree may be selected and termed dwarf if they mature to a natural size that is significantly smaller than the species. In this situation, the term dwarf only refers to the fact that it is smaller than normal at maturity. So, you could have a "dwarf" tree that grows to 60 feet while the species is usually 200 feet. It is a relative term.
There are many different kinds of ornamental cherry trees, some of the cultivars that originated in Japan are weeping forms and some are not, and some mature to a smaller size than others. To identify a specific tree and avoid confusion you would need the botanical name and cultivar name.
Your zip code places you in zone 6A or the coldest part of zone 6. In an exposed or windy location it might be as cold as zone 5 so I would suggest you landscape only with plants considered hardy to zone 5 to be conservative. Prunus x "Hally Jollivette" grows to about 15 feet tall and wide and is hardy to zone 5, that is small for an ornamental cherry as most exceed 25 feet. "Snow Fountains" is a weeping cherry (Prunus x 'Snowfozam') that grows to about 15 feet tall and up to 20 feet wide. Specialty nurseries that carry Monrovia products may offer Prunus serrulata 'Kiku-shidare-zakura'(P. serrula interstem) that grows to about 13 feet tall. It is listed as hardy to zone 5.
All kinds of trees, dwarf or not, will thicken at the trunk over time. It is a sign of age, the increase reflects the number of annual growth rings every tree develops. There is no way to stop that from happening. The mature dwarf tree may be smaller in height and width than a non-dwarf tree as far as branches are concerned, but their trunks still grow thick with age. I hope this helps you with your planning.
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