OtisWinslow wrote:
snip

That's a good thing to pay attention to. You can also check it at
idle before shut down by briefly turning the switch to "OFF" and
see if the engine starts to shut down.

I've been taught this shtudown procedure, too.
But, what is the magic about turning them BOTH off, simultaneously?

If, at idle, you turned off the left mag, and noted an rpm drop,
then turned off the right one, and also noted an rpm drop,
then doesn't that confirm the same thing as turning
both of and feeling for the engine to start to shut-down?

Although, maybe it's just me remembering my student fubar
of once turning off both mags during runup, then turning
them back on, and KA-BLAM!