That people think equal isn't mean to be taken literally is fine (I also don't) , but the intent is clearly to portray Gaban as being relative to Roger and Rayleigh in his introduction. Except if we were all wrong and the dude is actually mean to be the Usopp of Roger Pirates living off frauding his way (role already taken by Buggy btw), then it's safe to assume he has the strenght to back that up.