There's a good chance a few cars do have Panasonic cells. My main gripe with ev car batteries is there's nothing clever about them, they are just plastic boxes stuffed full of 18650 or 21700 battery cells, laptop battery cells, or electronic vape batteries, same is in your power tools or robot lawn mower, hundreds or even thousands of them. The extra weight that must involve over something bespoke like a scaled up mobile phone battery is mind boggling. The big players in 18650 and 21700 cells are Sony, Samsung, LG and Panasonic, so pretty much any ev car will be filled with one of those