I think "no" is an extreme case "limited" is more likely.
Do we have a list of which airports UA uses GGG for catering vs its competitors (NewRest, Sky Cafe, LSG, AirFayre, etc)?
I know IAH is NewRest and CLE is SkyCafe (with horrible branding)
Pretty sure EWR is GGG, not sure about IAD or ORD.