Ideally, the thing you do in an emergency is largely routine, so that it happens by instinct rather than being a special case you need to remember. It should not be different in arbitrary ways.
For example in both trains and cars, thanks to anti-lock braking, the correct way to stop the vehicle ASAP is to brake just like normal but as hard as you can, the computers will automatically solve the much trickier problem of turning your input into maximum deliverable braking force by periodically releasing brakes on sticking wheels.
If you run a fire drill, it's surprisingly difficult to get employees to use fire doors that they're used to finding alarmed and unusable. Even though intellectually they know that, say, the door at the bottom of the stairwell is a fire door, with crash bars and leads directly to the outside world, and this is a fire drill, they are likely to (for example) exit on a higher floor and go through a chokepoint lobby, as they would normally, instead of following this safer path that is emergency only. Sadly it is hard to fix buildings after construction if they were designed with such "unused" emergency exits.
For a backup process, having restoring machine images be a service that is sometimes, though not constantly, used anyway for some other reason, is a good way to be comfortable with how it works, that it works, etc. At work for example we routinely test upgrades on test servers restored from a recent backup. Restore serviceA to testA, apply upgrade, discover upgrade completely ruins the service, throw testA away and report this upgrade is garbage. But in the process we gained confidence in the restore process, infrastructure people instead of trying to recall something they only ever did in a drill, when things go badly wrong are very used to this procedure because they do it "all the time".