I wonder how many folks have the reflexes to pop their Rivian in neutral as quickly as they can release the accelerator. Actually shifting the Rivian to neutral requires looking down, at least for me, it is a bit finicky.
I agree that snow tires--especially the Haka R5--would almost certainly have helped. Even an All Weather, 3-peak-snowflake tire is better than an AS tire. Ice sometimes happens in places with mild winters and sometimes happens outside of normal winter months.
With most issues in life, causation...
Down shifting and regen can be feathered, but they do not have the ability of ABS to keep the car going where it is pointed. When drivers have multiple cars at home, radically different inputs and behavior should not be required when traction is lost in an emergency situation...especially true...
Even Minnesota doesn't get enough to practice often. Also, although feathering the accelerator enough to disengage regenerative braking can work, it is really a tricky thing to do in a sudden emergency...and most of us drive other cars that require very different behavior, so it is near...
I am really sorry this happened to you. I agree with your premise that even low regenerative braking can induce a slide.
I posted this thread in early December discussing this exact issue:
Snow Mode--still too much regenerative braking
I have a friend that just bought a Bolt and doesn't have a home charger. There are a number of free level 2 chargers close to his house. He can charge while in Walgreens, the liquor store, the grocery store and two different malls. He also can put 50 miles on overnight plugging it into an...
Drop some kids off at home after practice at night or drop a friend at the airport...watch them grab their equipment bag or luggage out of the back, and search for the button...then give up and manually close it. This happens nearly every time. It is a real issue, though certainly not a big one...