Musk did not found SolarCity; that was Peter and Lyndon Rive.
I don't know what "found the Tesla as it exists now" means. Founding and leading are distinct. Musk has been a key leader at Tesla; he was not a founder of it or any merged or acquired company.
Founding is not the same as incorporating or being the first to work on. For example, the founding fathers of the USA were not the first people to live in the thirteen colonies, and many of them were only involved with some part of the origination of the country.
I have to imagine you know that isn't what anyone else means by "founding a startup" and that the original 13 colonies weren't the United States (that's why they had to "join or die," they viewed themselves as separate and independent states, even in competition with one another). You've invented a new definition to suit your rhetorical purpose. I think you can make your argument without this frankly dishonest tactic. I've seen people make the same point here on HN many times.