Tesla is the only one that boast's exaggerated rated range figures based on the best of the best of the best possible conditions. Almost nobody in Tesla gets the real world range out of it. Tesla doesn't pay for marketing, so they pull tricks like that to generate buzz. Has worked very well for them. Yay to them. But, better range rating for a Tesla would be take what they say, calculate about 75% of that, and you'll be fairly close if you drive reasonably unaggressive. Ford on the other hand, including several other EV makers, choose to underestimate and surprise later when owners see much better results in the real world. Ford's 300 battery with no load, will likely be in the 350-400 mile range! maybe $425+ if in perfect weather. Porsche, Audi, Chevy, all end up keeping their customers happy because they can achieve rated range in normal conditions. Tesla forums are the only ones where you get 10 people asking daily "what happed to my range?". "What's wrong with my car?". etc. They're also the only one that doesn't provide range variations based on your driving stile, where you're going , etc. Same algorithm used every time. Pretty much useless. I just leave in on Percentage reading and treat it like a gas gauge. That way I'm not annoyed every day when I charge t0 300 miles in range, drive 30-40 miles and pull in the garage with 200 miles of range left. I like the way every other ev maker on the plant uses predictive algorithms to provide you with more realistic range figures that you'll actually achieve in daily driving.
OK, that got long. point being, don't take range figures as gospel. They can been useless in a large majority of cases. Research real world tests. I hope Rivian didn't follow the same Tesla approach. sounds like they didn't adn we'll have predictive range estimates that you can actually rely on.