"flames under control within a half hour" is impressive given all the stories I've seen of other EV's lighting up and batteries going through "Thermal Runaway" where the firefighters essentially need to wait for it all finish rather than try to extinguish.
I just got off a chat and it sounds like they know it's a problem but don't have a fix right now.." For the concern you have described, this is something that Rivian hopes to address with a future update. Unfortunately there is no set timeline."