If you want to know about the possibility of graft incompatibility ask a
nursery owner that grafts a wide range of paw-paw varieties, it would
probably be more useful than searching the literature.
Nick England or Mike McKonkey come to mind.
I find this theory doubtful only because I haven't heard of it being a
problem when reading comments over the years of scores of hobbyists that
regularly graft them. Sometimes the people that do have information that
people that read about doing don't.
[nafex] paw-paw graft incompatibility,
Alan Haigh, 11/23/2020