exactly so it's not my rule of thumb you're disputing at all -- it's whether to apply it in that particular case.
but that's the whole point of a rule of thumb --- it's not invalidated by any single instance
That particular decision is the only 30-1 case I have ever seen. More often it is purely partisan opinion, when a rule of thumb is no help..
I have quoted before a game where the referee failed to turn up and a random spectator volunteered to referee. When he penalised his own team for not being back 10 metres at a 22 dropout, along with other weird decisions, we realised he really did not know what he was doing. The teams quickly decided to try to referee the games themselves, the captains telling the referee when to whistle. He seemed happy with that, and we had a game of sorts.
On another occasion I was running the line for a friend on a very wet day. The ball was kicked towards touch and a player fell on it, sliding perilously close to the touch line. He had his eyes fixed on the line and realised he had stopped just short of it, so he got up and ran off. Unfortunately in so doing he had stepped right on the line, so I flagged it. He was furious, but in the bar afterwards I explained it to him. He was still disgruntled!