In this case Tesla isn’t going to be making the standard. SAE and IEEE are independent entities that don’t have a stake in the game. Federal and state governments aren’t going to let one company without independent verification determine when a vehicle is ready for prime time.
IBM sought out Microsoft for and operating system for their new PC. As part of the agreement Microsoft was able to license their operating system separately from the PC. At the time IBM (wrongfully) thought that the money was going to be in the hardware (NOT software). The writing was already on the wall. Hardware was getting cheaper and software was getting more expensive. It was only a matter of time when they’d cross.
And no matter what happened with IBM and Microsoft - the end product didn’t have the potential of injuring/killing people because of a software bug or hardware glitch.