Seeing their activities, I feel like if I could work there, that is, if I were an employee of this American restaurant, I could probably earn Bitcoin very easily, anyway, in your opinion, is it more convenient for those working in this company to accept Bitcoin or fiat as payment?
Maybe you didn't understand the information you posted, they are not going to pay their workers in bitcoin, they are only going to pay a bitcoin bonus of $0.21 per work hour to all the hourly employees of their company-operated restaurants and this can be only claimed after two years.
let's take for example you work there 10 hours daily for 5 times a week, then you'll be earning an extra $52.5 worth of BTC weekly which you can claim after 2 years. It only seems to me as an avenue to DCA $52.5 into BTC for a 2yrs period if the worker is going to remain there for the said 2 years.