"Bend" in this case, refers to his ability to bend around toward a pass-rusher trying to blow past him on the outside. Which is, in fact, good in Campbell's case.
He played almost exclusively in a two-point stance (and a high one, compared to most tackles), and even when he was in a 3-point stance, never gets all the way down.
Guards play almost exclusively in a 3-point stance, and have to get under defensive tackles at the line.
I don't think Campbell is a bad player, and maybe he'd be a pretty good *right* tackle in the NFL. But saying 'just kick him in to guard', the default answer to when tackles have short arms, I don't think would translate in this case, because of how he plays. And I think his arms and wingspan are too small to play left tackle at a reasonably high level in the NFL. He has good feet, good power, and good bend, like those four articles said, which, playing on the TE side at RT, might make him be able to be a good pro.
I don't know if you want to necessarily draft what projects to be a right tackle only at 4.