Plato would not have made such a dumb geographical mistake.Well, it's not my place to determine Plato's geographical accuracy. But 9,000 years of verbal memory strains my belief zone.
The description of location is not a likely change even from oral history. From an island a few miles from the Greek mainland to one specifically set outside the pillars of Hercules does not seem to be the kind of mistake one would make.
Plato claimed that this story comes from Solon's discussions with the priests of Eygpt who had written records not just oral ones.