In MLB the Show's Diamond Dynasty, there is a card set for Real 99. These cards are all 99 overalls, but they might not coincide with that player actually being that good. For example, recently DFA'd Anthony Bass has a Real 99 card, but he's far from that good in the game.
Elly de la Cruz has one, too. While he is the most exciting prospect in a long while, he's not a 99 overall, at least not yet. A lot of minor league prospects have these MLB the Show Real 99 cards, too.
It's not unnatural for MLB the Show to offer high overall Diamond Dynasty cards for players who might not deserve them, but there are a lot of these cards and most players can't get them. The reason is that a team with this card is a real baseball player's team.
Explaining the Real 99 card set in MLB the Show
If you encounter a Real 99 card in an opposing team's lineup, it means you've been matched up with that player. If you see the Andrew Painter card, that means the person with the other controller is the Philadelphia Phillies prospect.
If Grayson Rodriguez's 99 card is in the lineup, the Baltimore Orioles pitcher is actually playing. Any time a Real 99 card is present in MLB the Show, it's designated for that player.
No casual gamer can get these cards unless they somehow make their way into Major League Baseball.