You can still learn a lot even if you don't graduate.
There are far cheaper ways of proving somebody can read, write & reason but for some reason employers seem to be stuck on that University diploma. I guess it's easy for them.
I suspect this test is the single biggest reason for the success of the company.
I suspect any reasonable test in that general direction would do the job. I don't think they use it to specifically hire the people who achieve the very best scores, but rather to not hire the ones who perform poorly.