When he told me this, I thought he was talking about ASCII, but I had to actually double-check with "man ascii", because 5B/5D sounded familiar but wasn't 100% sure he was right.

But the point is not that he memorises the ASCII table. The value is that he learns that computers internally represent letters/punctuation as numbers. The underlying concept is what's important, and the learning of specific values is mainly useful as a way of learning and reinforcing that underlying concept.