Salaried workers are office-based. Hourly workers are factory-based.

That actually clarifies the whole circus Musk pulled. He announced that anyone not coming back to the office (which obviously does not apply to factory workers) is effectively tendering their resignation. Then Tesla announces just days later that a 10% layoff of salaried workers is going into place. This is typical Musk behavior in that he tries to control narratives by pre-empting them. By sending this email out and then announcing layoffs later, it sets the narrative that it's an employee problem, and not a Tesla or executive problem. From what I saw of some reports of Tesla employees, Tesla doesn't even have enough desks and parking spaces for everyone to come back to. Musk knew what he was doing.