Me I think they should be able to answer any question, even stupid ones, relating to their portfolio. A functionary can do it. But the buck stops with the secretary.
A health secretary should be able to explain why a dispensary is lacking drugs. Agriculture secretary should be in a position to explain why a certain dip has not received chemicals.
If not, they should promise a status report. It's their job. It's not a reward or a title of prestige.
As long as there is a process. Perhaps one would require them to appear before the committees a certain number of times every year.