Its really dependent on the candidate and the position. A quality senior engineer may be gauging the feasibility of ideas that may take _years_ to come to fruit

Its really dependent on the candidate and the position. A quality senior engineer may be gauging the feasibility of ideas that may take _years_ to come to fruition. That requires a lot of non-technical information and both trust and a good working relationship with sr. management. If they are not willing to freely share information, they probably won't utilize the caliber employee who would typically request it. Its no guarantee but personally when I've interviewed people who have asked these types of in depth and / or difficult to answer questions they've turned out to be orders of magnitude higher quality. They know what successful companies look like, and aren't interested in taking chances on companies that won't or can't utilize them to their potential. Doing so requires sharing enough information and trust that the employee can help steer the ship.