It's possible that the Robert Johnson who died in 1733 is a different person than the Robert Johnson who married Katherine Allen and had a daughter Mary, as seen in the deed from 1692. Presumably that gift was made when Mary married James Johns(t)on. There is, however, no proof that there were two Roberts. You are saying "based on the available information it is more likely these two are different men." I'm not sure what that information is.
One red flag, of course, is the presumption that Robert Johnson lived from about 1643 to 1733. Making him 90 years old when he died. Unlikely, perhaps. But I'd like to point out that my 4th great grandfather James Allen Johnson lived to be 98. He lived from 1747 to 1845.
In either case, however, it seems that Mary should be connected to Robert Johnson who was married to Katherine. And the only thing in question, I think, is the Robert Johnson with the 1733 will.
Thanks so much for your input.