The post says "cruiser ready" (magazine loaded, chamber empty). Carrying a shotgun with loaded chamber in a vehicle is not considered a safe action. Also, in many states it is unlawful to have a long gun (rifle or shotgun) with a chambered round in a motor vehicle; probably an anti-poaching law, but very much a common sense safety precaution.

At home my 870 has a full magazine, empty chamber, action cocked, safety engaged. In order to use the shotgun it is necessary to hit the slide release, chamber a round, then disengage the safety. With practice and experience this takes only a second or two. In my opinion the added level of safety in storage and handling make this worthwhile. YMMV