He also received a call from Tesla to check on him. The advisor said that "it is a known issue in the Cybertruck that when you do a screen reset, instead of resetting in the standard two minutes, it takes five hours."
“Car wash mode” just folds in the side mirrors and puts the car in neutral. The need to reboot car is probably coincidental unless there’s some sort of extreme panel gap that let water in and caused a short or something.
It's probably something bullshit to fight off lawsuits - "the computer says you weren't hopping on one leg, dancing and throwing salt over your shoulder, and you didn't activate car wash mode, we can't help you sowwyyyyy". Manufacturers don't want to fix on warranty after all.
Cars haven't needed a car wash mode for a century, but thanks to Tesla innovation you need to remember to toggle a switch before washing your car or it'll break.