The 'Sit on your hands' advice is not in regard to flying the aircraft, its about not over-reacting to indications and jumping to conclusions. Obviously if the AP is handling it, no issue, if not the PF will have their hands full, but last thing you want is the PM flinging switches, knobs and levers before they've assessed what is actually happening. As JT said earlier there are many scenarios that could occur outside of certification standards and you deal with them as they happen, but a bog standard engine failure with no severe damage is going to be almost routine for a jet crew. The other stuff should be rare if the aircraft is well maintained and so on.