If Florida laws are typical, they would basically be that if the cocktail-napkin "will" was indeed written by the decedent, the property division stated thereon is legal. If the cocktail-napkin "will" was written by someone else, it isn't.
So returning to the hypothetical scenario, if the "will" were one that most people would regard as an obvious fake, but Greer accepts the word of one 'expert' who proclaims it genuine, would it be legal for Greer to award the decedent's property on that basis?
Why don't you just ask me the question you are really searching answers for? I doubt if it has anything to do with napkins.