G[f_, Except[f_]] := 0
    
    With[{u = {f}},
     HoldPattern[G[f_, Except[f_]]] :> u
     ]

gives

> `HoldPattern[G[f$_, Except[f_]]] :> {f}`

I would expect

> `HoldPattern[G[f$_, Except[f$_]]] :> {f}`

Bug?