The Rivian has a great crash protection rating but if you get hit on something attached to the hitch receiver it will transmit that energy to the passengers so it not a great idea to leave anything in there when not towing. Let the crumple zones do their work and maybe save your life.
The video was about DC fast charging on a 3,000 mile road trip with some free opportunistic AC charging. All I can say is I picked a nice route the Rivian adventure network is fast and free and the Tesla Supercharger magic docks just work!