A close relative, sure. But to point to reading comprehension and go on to elocute about that would not have basis in this example, in my view. The crux of the issue literally isn't written, as you say, it is assumed. The point being it is an implication from fully external understanding. It isn't that there is an inference to be made or dots to be connected based on notions only vaguely referenced by the text, e.g that the value could be equal / that dice rolls being equal is a valid answer. Because there is no vague reference in the text. Correct understanding in either case fully depends on understanding of concepts outside the text. The person with the best reading comprehension in the land would be unable to comprehend the text without that external understanding.

To put it more succinctly, if comprehension is understanding stuff, reading comprehension is understanding stuff based on what is written, right? The issue being that in this case the lack of comprehension is about something that wasn't written. It is a comprehension issue unspecific to reading.