Again, it all depends on what restaurant. Some don’t have an expeditor. Some do. I’ve known restaurants that “require” servers to clean the bathrooms, should it ever get “slow”. If there is a way for management to cut costs, they’ll do it. If that means making sure a higher cost line cook is spared from doing what a server can be tasked to do, that manager will make an economic decision to task the cheapest laborer to do it. That would be the $2.13 server.
Yes. I am a firm believer in adding the phrase “and all other duties as may be required” to all job descriptions.
The “expediter” job should fall on a manager if necessary.
As a line cook I have had to do other things besides cook.
Bathrooms usually fall under the auspices of the dishwasher or waitress.