It's probably because there are both Intel and amd Tesla cars. Newer models use AMD

The vulnerability is much more of an issue for Tesla('s profits) than the owners. It's not a simple exploit and not the worst concern for average users of those chips. You have to have physical access to it in order to exploit it, as well as a system worth hacking (think, national security trying to prevent compromised personnel from physically using the exploit on their systems). I'm not worried about someone breaking into my house to physically hack my computer, just to find some memes and bullshit

It still has to be addressed by both Intel and AMD, because that's their whole industry. But recalls and such aren't needed, because bugs can be exploited all over the place and this one isn't a high level risk for the average end-user. It's more of a concern for Intel/AMD reputation and the large industry users of their chips