I have an old male D. virginiana in my yard that puts up a lot of root suckers, but I’ve never had any success grafting kaki scions to those root suckers after trying dozens of times. The grafts always look like they’re taking and then die back after a month or so. I’ve had good success grafting to the root suckers of purchased kakis grafted onto D. virginiana.
Some of my purchased kaki trees succumbed to what looked like SDS (sudden wilting on portions of the tree, blackening veins in the leaves prior to wilting, spreading throughout the tree). Whenever I tried to regraft to the D. virginiana rootstocks of these trees that died back, those grafts also failed. The rootstock suckers never showed any of the symptoms, but maybe it’s some kind of disease that D. virginiana can carry and transmit without exhibiting any of the symptoms. Perhaps most of the older trees in your area (and maybe in my area too) have already been exposed to the disease and carry it, but it doesn’t get passed on through the seeds. Just a theory.