Well, if it was Devil Hulk you could say he could say he smelled a liar.

But yeah, probably the takes one to know one. Fixit has been lying to himself for a while now (he was in the shadows, admitted to Betty that he loved her, owned up to leaving Bruce in Hell, the favor he offers McGee at the end)

I think the whole run is a fascinating examination of the Banner system.. as he says Bruce makes peace with his Devil/Father and grows. Devil makes peace with the other alters who were trying to kill him last time.. Joe and Childlike grow closer despite traditionally being paired against each other.. Alters cant die anyways, and you can have alters merge without the whole system integrating.