I took it as an exaggeration to make a point. They're unlikely to ask you to do that--or to pay you for doing so. But within the broad confines of developer, or product manager, or technical marketer, the is a wide range of roles and responsibilities. If you've been working on a mainframe and your employer decides to retire it but is happy to put you on some front-end web stuff which you've never touched, that's probably going to be a tough adjustment that may not end well.

Unfortunately, all too often in the US, there is no contract. You apply based on a job description that can be changed at any time by the employer, and has no legal force in any case.

I did have a job at a very small defense contractor, where I was 99% a software engineer, but when we had to move the safe (happened twice) as the largest man in the firm and still reasonably fit in my 20's -- I also had to do that.