For safety's sake, Stallie... that rule is designed to keep you honest AND alive...
Honest, in that ATC may approve an early turn due operational reasons, but it doesn't happen all that often. When there is no "3rd Party" (ATC), such as your 400-odd metre collection of rocks and sand out at Wheelmebarrowback ALA, the decision is taken out of your hands and legislated... for safety's sake.
RWY surveys & etc aside, i believe this rule is more designed towards losing a motor once you're airborne... singles speak for themselves- you'll be making yourself very busy trying to recover from the turn while finding a spot to land... and in a light twin your performance on one is negligible at best, let alone after losing the "low" motor in a turn at low altitude/low airspeed and trying to recover to the correct attitude battling an increased Vmca and making all that extra drag in the process. Really is best to keep as much of the odds in you favour right?
Me thinks you knew all that already... but you did ask
HJ