Board Thread:Questions and Answers/@comment-24975288-20140809171550/@comment-4714517-20140815085206

It hinges on the fact that TOAA was conceived after the retcon, when B lost OP status. Basically, the writer seems to have considered B to be OP and written story that way. There are holes in the comics, but it's basically Word of the God in this.

As for more than one OP user in the verse, the term gets thrown around pretty carelessly at times. Sometimes it seems to be pretty much description for the very top of the power-level instead of the very strict definition we use on this site.