I suspect that Namshiel was surprised by Marcone - Nicky had obviously been restricting him in his hosts and his time out and the information he received as Nicky didn’t trust him.
When let out for Small Favour, it was obviously in part to counter Harry, as well as to run the big spells. Nicky probably told him about a young punk wizard, and yet Harry still got the drop on him. He was probably only brought out to deal with Senior Council previously or other major magical heavy hitters.With Marcone Namshiel had access to the soulgaze Marcone had done with Harry years before, and had access to Marcone files on Harry. He was A LOT more respectful towards Harry in BG, because he considers him now to be more of a peer, and understands that it was possible for Harry to have got the drop on him (due to Nicky) Marcone gave him the information which Nicky didn’t to win Namshiels trust and turn him against Nicky.