While it's true one of the girls isn't a product of Arsenal until last year, there are 4 other girls who are (2 weren't called up for the U16 tournament). So there are a total of 5 players (2 '02s and 3 '03s) in the GNT pool, 4 are Arsenal "homegrown". That's still pretty impressive coming from one team.
The question is why Arsenal isn't killing it in 02 ECNL. They've never missed more than 2 GNT players for a game, and they have lost even with full strength. In addition to the GNT players, they have other players on the ODP team, yet they are currently 5th in the 02 ECNL SW standings...