I know measuring power in amps is against everything high school physics told us, but it's a really common approach in electronics engineering. They literally do that all the time.

I think a sentence or two later the official site gives an explanation why: lipo battery sizes are measured in mAh, so dividing battery size by current you get hours of operation.

I'm still a noob when it comes to microelectronics, but my understanding is almost every chip runs on 3.3v, lipo batteries are 3.2-3.7v depending on charge level. When they talk about power in amps they assume everyone knows they mean at 3.3v