gin rummy edge (mostly) comes from?

[mosta]

so I read about how Stu Ungar dominated the game. one big part of his game is that he knows every card that's played, perfectly. is that enough to be the best? putting the question another way (maybe a bit different): does a simple computer program, that accounts for every card played and implements a simple heuristic system to guess opponent's hand, beat the best player? or is reading the opponent's reaction and how they hold their cards essential to being as good as Ungar was? (this is just a theoretical question--I've never tried to play this game seriously.) related question: is it unusal for a top player to be able to remember every card?