They're free to work elsewhere and are adults and responsible for their own income. If they're upset with the conditions at Tesla enough to want a union they could just work elsewhere instead.
Doesn't say anywhere they can't take them just that some are claiming they're skipping them to keep their performance up don't think we should just taking their word on face value. It's just a statement to try and make their work expectations seem unreasonable when we all know the real goal is to lower expectations and raise pay at the threat of halting production.
I'm by no means a Musk fan but its a free country, Tesla shouldn't have to be held hostage to these people, no ones forcing them to work there.