Yeah that is how they test your shut-off switch they flip it off while it's running to make sure it shuts off. If it doesn't then it's pretty much useless. My 6AL is about 25 years old since I sent it to MSD when I bought it used to have them extend the wires and check it out. I am aware of how voltage spikes can damage electronic devices and I'm not saying it can't happen but tech inspectors do this to thousands of cars every weekend.

Gus

The MSD tech guy told me what kills them is reattaching the battery cable while running - if I recall he said it goes full field while disconnected then zaps the box when reconnected. I’m no electrical expert, still haven’t forgot my first electric shock.

Yep they check it the same over here too. The battery isolation (kill) switch should turn everything off and the engine should stop. Removing the battery cables while the engine is running will still allow the engine to run IF the alternator field circuit isn't interrupted. This can cause voltage spikes as the battery acts as a type of voltage "buffer".
I've had no issues with either an analogue 6AL or a Grid when the kill switch is checked but on the grid we do have a MSD filter (capacitor), which we also take the voltage supply for the Racepak from. This filters out any RFI or relay spikes though we've fitted flywheel diodes to the relays where possible.

So if your kill switch works properly, this won't be an issue.

Never had an issue, first started racing in '96 and they check it at least once every season. I'm always switching it on and off too but usually the car isn't running.

Let me re-state my earlier post.

Early MSD without full time +/- wires, engine RUNNING - disconnected the positive battery cable and reattached it and the engine stalled, could not relight it.

Checked for spark - none. Called MSD and the tech said I fried the MSD because of what I did. HE said I ended up full fielding the alternator and killed the box.

Sent the box in they said it could not be fixed.

This was probably in the late 90’s.

No clue if the newer boxes are protected because of the full time +/- wires and no clue if using a relay to use a kill switch would prevent this or not.

Yeah, I can see that happening, sorry to be a bit long winded here. Disconnecting the battery while the alternator is charging the battery, will spike the voltage as the alternator is unloaded. Full fielding is some thing auto electricians do to check / test alternators, it involves bypassing the field regulator and applying 12v to the field which can bump the o/p to over 28v.
According to MSD, their ign units, (at least the newer boxes) have a built in regulator and are recommended to work from 9 to 18v. Momentary / short periods of 24v (jump starting) are ok.
I have an old (1996) 6AL that has been used on various cars / engine combo's, it has it's own battery supply cables so I'm guessing that was around the time they changed.

one thing i NEVER do, is disconnecting the battery cable [either one] while the engine is running.
if one needs to diagnose electrical problems, there are a multitude of better ways than doing this !

Unfortunately a battery isolation switch is an NHRA / FIA requirement if you want to race at "permit" meetings here in Europe and the UK, I think it's the same in the USA. There are ways to minimise any voltage spiking risks though. They usually check it with the engine running and it must cut power to the ignition, stopping the engine.