Pikman, maybe you guessed right...? The spacial reasoning tests are an indicator to be able to manage left and right regardless of disposition on the radar screen; also about mental processing, good tetris players are probably good ATCs.
But I agree with your comment about not being conclusive; we think we know what we want, cause that's what we've got, therefore we try to identify that in these tests... When was the last time real ATCs did these tests to set a benchmark...? Would that be a true reflection of those individuals at time of recruiting, or what they have learnt over the years...
But there is some validation, based on recruits getting through... Is that a true test, maybe anyone can get through if trained right...? I have seen plenty of hopeless trainees that did get through the tests and thus were recruited, but were never going to make it, well maybe if you had a 5 years training program, so what does it highlight, my bad training skills or bad recruiting tests and processes...?