Not overcrowded, just short more than anything else. I mean, they'll have the sense of not really having unlocked all that many techs because the game is over before they really have a chance to do so. It might also make the game easier in a number of ways, because they can get to the AI strongholds so much faster, especially with three of them all at once (and the AI will never get that large).
And it also takes a lot of the Grand Strategy aspects of the game right out, because there aren't too many difficult choices to be made in such a small map. So it's good as a learning experience, or as a fast-and-furious way to play the game, but I wouldn't call it representative of the "real" experience. It's certainly a valid way to play, and I think they'll continue to have a lot of fun, but it's like playing Civilization on just one continent through a few of the ages. Very similar to how that subsets the main game experience.