Does the reset change the SOH number? How long does it take for the SOH to recalculate?
Yes, it goes to 100%. The amount of time the BMS takes to 're-learn' the actual capacity varies, I believe, with how much the car is driven, although there is probably a time element as well. I'd guess about a month, but if there were two or more bars lost you wouldn't have to wait more than a week or two for one to drop, in all likelihood. As for Carvana not doing resets: probably not, but whoever is "upstream" of them might. Lease returns often go to car auctions, and car auctions are not exactly Hotbeds of Good Citizenship.