Interesting, how did you arrive at your conclusion that the owner knew that he was responsible for the damage? He says that he can't remember any deep puddles on the way there, but even if there was a few deep puddles, the car should be more than capable of handling such water depth anyway when being driven. If the car was left standing in water and the battery was submerged for an extended period then I could accept it, but then, the car itself should be wet inside as well?
Maybe he was thinking, when he said that was expecting a bill was because the car's warranty had expired and something had become broken?
I don't know for sure, as indeed, none of us do, that the battery had been submerged, but even then, I would think that it's not unreasonable to expect that the battery should be properly sealed to prevent water ingress anyway?
Seeing as the batteries are mounted low down, that surely is a negative for electric propulsion if the weather starts to rain like we get from time to time, really heavy, that you will have to seek out high ground and sit it out or even stay overnight etc, in case there are deep puddles on your route?
How are the emergency services also going to cope responding to 999 calls in the future if puddles that are currently OK with ICE vehicles to drive through in perfect safety, without hydro-locking their engines?
It sounds more like Tesla, are doing what many companies do, and that is trying to see how much they can get away with, which seems to be a common theme today.