Notice that your criteria for impressive cleverness excludes practically every graduate student -- the vast majority make next to nothing, have few "concrete" things to show off, etc.

It's not criteria for cleverness, it is criteria for evidence when the prior is 0.0001 (for 1 in 10 000) . One can be clever at one in 7 billions level, and never having done anything of interest, but I can't detect such person as clever at one in 10 000 level with any confidence without seriously strong evidence.

This is substantially different from EY currently being a math prodigy.

I meant, a childhood math prodigy.

In other words, he's no better than random chance

If Marcello failed one time out of ten and Eliezer detected it half of the time, that would be better than chance. Without knowing failure rate of Marcello (or without knowing how the failures are detected besides being pointed out by EY), one can't say whenever it is better than chance or not.