Different genre go about differently about monetization and progression.
Therefor a practice in one could be considered P2W where as it wouldn’t in another genre since other factors would come in and counter-balance the effect.
Simply put, we need another study on specifically bought games. Otherwise everyone definition are equally true.
In the meantime, it is utterly pointless to argue over what if WoW is or is not P2W since there is no consensus over what P2W for this game model.
Per Wikipedia study, this exercise was only done on F2P games.