As with Tesla, Rivian is being judged by its hoped future successes, not its actual track record to date.
(NB: I own a Tesla Model 3 and have the various "self driving" options.)
There's not nearly enough data to make a claim like that.
Safety features can also be considered a convenience, but that doesn't mean they aren't safety features.
Humans zone out, they get tired, they have slow reaction times, they only have 2 eyes, they get complacent. Computers do not.
I mean if you're right and reaction times are all that matter then we don't actually need self-driving cards for the safety benefits, just somewhat improved emergency collision avoidance/braking systems. Much easier problem to solve.