To me, evidence of a 'Ballmer peak' would be any evidence of high performance. If this was the only study, which for the comments it is, I would say this leads to an idea that the 'Ballmer peak' is on average slightly lower skill level at the point, but a larger standard deviation of skill level, leading to occasional brilliance while consistent performance is slightly worse than at 0.

I haven't looked up what the actual 'hypothesis' of the Ballmer peak is, but this shows that some elements of high performance could exist and that kind of thing leads to rumors, plus fun experimentation.