A mechanical engineer will probably not be called upon to operate any particular mechanical device. They will be called upon to either design or maintain it, both of which will require substantial mechanical engineering knowledge. Operation is a totally different thing for a totally different group of people. Think of the difference between a frontend developer and someone who might use wordpress or wix.
Having said that, you hear the same complaint from mechanical engineers as you might be seeing on any hackernews thread about interviews and hiring - no one ever uses the academic knowledge in real life. And this is true, I've never had to use a Bode plot or whip out a stress-strain curve. But I've had to work with technicians and while several are very intelligent and capable, there was a noticeable lack of refinement in their thought process or lack of breadth. I suspect it's the same thing with programming jobs (although I haven't had one yet, so feel free to call me out on it). Knowing CS will help give context that allows for a more refined programming acumen. Is it necessary? Probably not. In my engineering case, both technicians and I did our jobs equally well, although I often had more responsibility. But if your brand is to have culture of incredibly deep thinkers, you probably want to interview for this quality.