You're MacBook Pro battery doesn't qualify for any battery exchange because there is no battery excahnge for yours. The battery exchanges are for batteries that may have issues with heat and possibly explosion or fire hazzards.
Your problem with the battery is that it seems to randomly fail. And your battery is under warranty.
They make acceptions to the 90 day phone service for a few reasons:
1. sometimes the actual purchase date is not clear
2. customer service, listen to the customer, sometimes it's an easy solution like this one
3. fixing a problem fast is often cheaper for apple than dealing with an unhappy customer later
BUT... remember in most instances they will recommend you still take your computer to an Apple Store to someone can verify the problem visually.
You had a good experience... doesn't mean everyone should ignore their warranty agreements and call Apple demanding new batteries though. Remember, they weren't obligated... they just went above and beyond.