I've seen a lot of theory based on this and many people saying so; however, I'm curious as to where it comes from (if there's any official source) or if someone just made it up.
The best hint I could find online was in a discussion on the One Piece Wikia pointing out that it may have been an old Jump Fiesta interview:
It was allegedly in an old Jump Fiesta interview (2009ish), but I haven't found a source for it anywhere, and the translation has been disputed (it may have referred to a temporary ally like in Impel Down/Marineford War, rather than an actual crew member). Zodiaque 10:36, June 7, 2012 (UTC)
As long as there isn't a trustworthy source, I'm inclined to believe that Oda didn't mean CREW MEMBER.