Well... the majority of the work for ALL mods has already been done by TW, got to give them that. Without the base game, we would be lost sheep.Maybe. Maybe not. First, it's an entirely idiotic topic because it doesn't help at all.
Second, we don't know if it's true. What if the majority of the coop mod is based on development already done by TW? In that case TW would be amazing? Personally I have no clue. Unless someone has some deeper knowledge it's a pointless discussion.