All true but what makes you believe that they might not be honest? Even a Chinese/Korean gamer who pays on an hourly basis has an account and effectively a "subscription" if he/she logs in on a regular basis. It's not like Blizzard are saying we have 8.5M x $13.xx (as a possible average subs price) subscribers. They are just saying "worldwide subscriber base". Nothing more, nothing less.
There is in fact even the remote possibility that they are not counting Chinese/Korean accounts. Maybe they are indeed only counting "real" subs. Who knows? They could be "lying" about the numbers to their own disadvantage.
I don't know what the truth is. Just saying that it's unfair to accuse them of not being honest unless you can prove it.