Kind of makes sense. The raw numbers mean little, especially with Asia moving on. For all we know this 5.5 number has been their benchmark in subscription regions for a while.
Not to mention the token. A few people said it already but the token is a $20 sub. It makes guessing how much monthly cash they are bringing in even more skewed. Blizzard makes more money if 3 of that 5.5 are subbing with tokens than in a world where all 5.5 are paying normally.