that is wrong, there are communication protocol standards already. a quick google search could tell you that.
https://medium.com/@wiprodigital/talking-cars-a-survey-of-pr...
perhaps you haven't seen the xkcd about standards? i can google it for you if you need.
my point was, teslas could communicate with other teslas (and waymos with other waymos) by using any proprietary technology or method they choose. and yet they don’t. they honk at each other at 4am instead.