I think the point of Robinson being redundant is the FO views Byron and Biz as long-term members of the team, and while that hardly precludes another bigman being a centerpiece, they felt like Robinson's strengths were already covered between the two B's.

As for drafting on "need" I don't think that was the case, but rather they probably viewed MKG and Beal or MKG and Robinson as equal or close-to-equal talents, and felt like MKG would have the best chance to grow on this team. We all know the whole drafting a PG when you already have a starter business, I think they wanted to avoid that mess again.