Interesting. First, the only things that are changed in the MLB Quickstart are the team names and some of the logos (first screen print). The players are all still real and on the correct teams. [
EDIT: Actually, I'm not sure about the logos; I have historical MLB logos loaded for my fictional player/historical MLB leaue and the quickstart may have picked up some of them somehow. Those are antique BoSox and ChiSox logos, for example.]
The second interesting thing is, you cannot just save and rename the old MLB Quickstart and try to start a new game with it in this version like I tried to. Take a look at the message that appears (second screen print). Sneaky.