Having 6.5 million on Azura's does not mean you would have received the equivalent on other campaigns in the same period of time. For example, in 1 week's time I have only gotten 1.15 million on Haderus, despite having Emperor and not sleeping well. Normal humans have only 600k on Haderus.
Azura's Star is extremely good for farming due to the massive blue zerg population. Good guilds can farm 60+ guilds like Chuck Norris with only 12-16 players gaining massive AP. This is likely what Walks did.

Can't imagine getting into the top 2% on azuras while only playing there for a few days. That's crazy