Samsung Vibrant launching on July 15 instead of 21?

We've just been tipped with a document claiming that the Samsung Vibrant -- T-Mobile USA's flavor of the Galaxy S -- is now slated for a July 15 launch (with devices actually shipping to stores on the 7th) versus the July 21 date that had been pegged at the official announcement. Interestingly, this lines up with a completely different document that's been slipped to TmoNews today, so we tend to believe it; question is, why the change? Is T-Mobile looking to get a Super AMOLED jump on the competition, seeing how all four US nationals are launching a version of the phone? On the outset, seems like it wouldn't be a dumb move, though we can't imagine many folks jumping ship and heading to T-Mobile to pick it up when they know they can wait a few days and get a virtually identical phone (or in the case of Sprint, an arguably even better phone) on their own provider.