I've frequently witnessed controllers doing incredibly helpful, generous, common sense and flexible applications of rules in support of riders - and have once benefited from this myself when arriving at a manned control around 6am having ridden straight through the night on a 600, hands too frozen to write, brain in that state specific to Audax - no matter what I tried to say, only inaudible mumbles emerged. The controller made an assumption that someone in my state, and only minutes inside the cutoff, had probably passed the info control even though the brevet card wasn't complete, and he wrote it in for me despite my incoherence. I almost cried in gratitude.
As a controller myself I might occasionally have appeared to have misread my watch when a rider could have appeared to a different observer to have been a minute or two behind the cutoff.
I've only ever once seen something and thought "hmm, that looked a bit generous".
As so often the case, isn't the most important rule "thou shalt not take the piss", with (to steal from LWaB) the penalty being a lifetime ban and AUK exclusion for anyone proven to have cheated?