While out on a cobweb busting bike ride, I realised, having recently completed an OPC, that the problem with a double engine failure in a twin is that you only expect it to be a single engine failure and don't immediately lower the collective! I would guess that by the time it takes to realise both engines have gone, the rrpm has dramatically reduced.
So on the 135, are you saying that an engine can fail to the extent that it becomes a net torque drag, without a command input, without a clear cockpit alarm? Strikes me as a bit of an oversight.