With the Giants, Sullivan was their WR coach, then their QB coach. McNulty was the same with the Cardinals. With WR's and QB's so closely tied, I'm sure there's a lot of cross-pollination of knowledge between both groups and assistants.
We cannot look at this as if it were a talent hiring. I mean, it might work out, but in no way is this guy the best out there to help freeman.
As you said, cross-pollenation. But is it more "devils backbone" or "Stinking hellebore?"