Hi Rispa,
As you research the lineage of all types of plums your will find that the Myrobalan plum (cherry plum) is found in one of its many forms on each continent. So it’s quite possible that all P domestica and P Salicia are related in some way if you go back to early times. Even Luther Burbank used P. Cerasifera as well as P. Simoni to create his many hybrids of the Japanese plum. While none can say for certain that this is the case, I suspect that all types have inherited the genetics of P cerasifera at some point in time. This is why I consider it as a superior cross pollinator, especially for early blossoming plums as are the Asian plums!
This thread gives a bit more for your research.
Dennis