From the article quoted, power leveling according to Blizzards terms is someone else playing your character. A free boost to 90 is not paying for power leveling since you are having anyone do the work for you. Even in that qoute, Blizzard says that would rather have players take advantage of in-game leveling boosts. This is referring to RaF and Heirloom for XP boosts, and SoR for a free 80 at the time. This boost to 90 fits in with Blizzards stance you and seem to ignore the facts that you posted your self.
Looks like their stance has changed
Today, they stand behind it.Originally Posted by Blizzard Entertainment
“Once you have tasted flight, you will forever walk the earth with your eyes turned skyward,
for there you have been, and there you will always long to return.” Leonardo da Vinci