Buy a single damn video card. [...] That's likely why he thinks it's retarded... it doesn't solve any problems that aren't better solved by other solutions.
I'm not seeing how a single video card will help solve the problem of teaching how to build a cluster out of multiple networked computers. Nor would it look nearly as cool, which is directly relevant to the purpose of (to quote TFA) "getting children interested in science and engineering". It sounds like what GCHQ came up with succeeds much better at achieving the goals in question.