Thomas Shey
Legend
I don't think we need game rules to prevent inconsistent ad-hoc decisions. That's kind of the whole point of talking about how we run games. Conversely, if the rules are so restrictive that it prevents a GM from inconsistent ad-hoc decisions, either I don't understand how that would work (which is quite possible) or it would feel restrictive to me as a GM.
Matters of degree matter. If I have to explain why that's true, I kind of doubt you're going to get it. And I'm not much interested in a GM who has to have such loose rules that they otherwise feel restricted, to be dead honest.
Basically, I don't see any reason at all a game should not have enough and detailed enough rules that having to make ad-hoc decisions (and to be clear, I'm not talking about deciding difficulty numbers though there ought to be enough guidance there there's rarely confusion) isn't an unusual case. If you do, well, that's you.