It isn't surprising that off road is covered in warranty. They may put limits in, but look at truck ads: most of them are showing people towing a heavy load, hauling big things, or driving off road - often more than one of the above. Sure that isn't how people actually use them (most of the time), but that is how they sell them. I haven't looked at Rivian's ads, but if they show their trucks doing something in an ad, then a lawyer will have no problem convincing the courts that because it was in the ads the warranty fine print was a misprint and that is acceptable use.