Magnecore plug wire company offers the same guidance in writing with regard to damaging a control module when an isolated circuit occurs via the fire signal having no where to go. I wouldn't be surprised if the same guidance applies to both bikes & cars.
I expect many have done so without dire consequence, but with my luck with motorcycle electrical stuff, I'd be the guy with the steaming circuit board juice dripping outta the control module.
Seems easy enough to keep a spare plug handy, and clamp it solidly to a ground while setting the idle. That way one could leave the working plug in the engine. That's one less steel into aluminum torque cycle as well, and you know we like that.
To each his own.
