The engine shut off requirement only applies to R/C combat, and is only in the AMA rules because the AMA rules are, for the most part, a verbatim copy of the RCCA rules. It is not part of the core Safety Code, and as such insurance coverage does not depend on compliance with that rule.

GMS is not the only engine manufacturer who has problems with shutdown, but they are the only manufacturer that lauds such a deficiency as a "feature."

As far as forcing GMS to comply, good luck! The number of engines they sell for competition combat is negligible compared to the number they sell for general aviation (including "club combat"). They're heavier and less powerful than most alternatives, and priced about the same as the popular Magnums and Norvels.