Sure. I mean the GM adjudicates things all the time that are not covered by the rules, and in those moments the GM is acting as a sort of game mechanic.
I am suggesting, as someone said upthread, that the GM has several functions, only one of which is adjudicating. When the GM is just deciding a result, for their own reasons unrelated to the rules of the game - that's not adjudicating.
That moment when the GM is *authoring* a result, whatever their inspiration for that - that's not the moment they are adjudicating.
I'd say my job as a referee is to adjudicate between the scenario, call it fiction or imaginary world and those in it, and the players actions.
I don't buy it. I don't think it fair to call it a "referee" when you choose the opposing force, the scenario, and determine the result yourself. If there were rules present, we'd have that to fall back on. But lacking them - again, it is a proper GM function, but I think calling it "referee" in this case is misleading.