> I have literally never heard of a Tesla bursting into flames while parked in a garage.

Maybe a quick search would help you find the answer for yourself before making such comment.

See for instance this article compiling a couple examples: https://www.thedrive.com/news/28420/parked-teslas-keep-catch...

Some of the occurrences are while the vehicle is being charged, some are simply when the car is parked.