Most job descriptions contain some version of "other duties as assigned", IMO with good reason.
No job description can realistically capture every responsibility; this language helps prevent bad-faith disputes when new tasks or responsibilities arise that aren’t explicitly mentioned but are 5 millimeters away from those mentioned and entirely reasonable to be considered as in-scope for an existing employee.
I think also it's the reality in most engineering roles that you will often have to pivot to new technologies, help out on unfamiliar projects using different technologies (e.g., work on the front-end for a bit when you're a backend engineer), etc. Some engineers aren't comfortable with this and it shows. This is how I understood the original comment, anyway.
Anecdotally: People who aren't flexible about their job description are some of the worst people to work with. They always leave the tough unforeseen challenges to their colleagues to handle. Kinda the definition of "not a team player".
As an engineer, I had a job at a small company where I sat by the office phone, answered it sometimes, and had to get the door for deliveries. Not in my job description, but it needed to be done.
