Even if they don't personally use languages that require this knowledge on a regular basis, the idea that someone could come through a CS education and not know it is pretty stunning.
Not being able to write code that performs memory management doesn't mean you don't know how memory management works. It just means that you trust your GC.
Much more relevant would be to ask questions about what to do if you're spending too much time in GC and how to tune it rather than how you'd perform your own garbage collection.
Much more relevant would be to ask questions about what to do if you're spending too much time in GC and how to tune it rather than how you'd perform your own garbage collection.