The writers of those genealogies indeed claimed that the god Odin did exist as a real historical person. But that doesn't mean that we have to accept their claim.

Similarly, anyone claiming descent from King David is indeed claiming that the he was a real historical figure, but we don't need to accept their claim.

As for tracing Odin's lineage back to the Hebrew patriarchs, that is of course a form of syncretism, where people who believe in multiple religions create a mix of them for various purposes.