I think it should be by choice per employee, not all want to accept their money via bitcoin because price can change anytime if it's inside a bitcoin wallet. $500 is still a big difference if price fluctuates. I would prefer receiving it half in bank then half crypto so the salary from crypto can be considered a long-term investment.
I think this is just an optional to their employees if they want to receive salary thru Bitcoin or not. They can certainly sign a contract with someone of which company that the payment for services will be done in Bitcoins but remittances to the government (payroll taxes, income tax and etc) will surely cannot be done in bitcoin.