This is still a very difficult area to consider. On one level, having a wide-ranging knowledge of techniques and production skills is necessary, flexibility being an important attribute. On another level, having such capabilities can result in problems and it is important to understand why.
At one time it was possible, financially, to employ sufficient staff for all departments and each person had a specific job. However, that has changed and accountants govern the world! Sometimes, for a production to be made at all, multi-skilling has to be considered. Multi-skilling should be dictated only by the script requirements, which in turn affect the schedule and facilities.
There are sometimes very practical reasons for some departments ...