It is actually the only way that carries no weight in the selectors talent. The person either gives up and stops working as hard or they don't and succeed. I actually help recruiters select talent for a living in corporate America with testing and data, and first of all I don't suggest them doing any of this. It is also not very feasible to do during the selection process in corporate settings amongst a bunch of other things.This is the opposite of what i want to see in somebody making personnel decisions because it carries way too much faith in that's selector's absolute talent in doing so and a need to do so that disrupts any hope of a positive culture. This kind of thinking is all the hallmarks of a terrible boss who alienates talent.
I do however know a lot of companies are turning to sending their teams off to be treated harshly in things like Navy Seal Hell week selection like programs. It does wonders for team building. In Deion's case from testimony of some of the people who got kicked out, he is simply doing this to weed people out fast that are quitters and forming that common bond for those that stay. Then once they are in, they are in and treated as family, while still being held to high standards.
It really is a fantastic way to select people who have a very high chance at success and building a strong bond between those that stay in a SHORT amount of time where you don't have the time to get to know them like in the High School recruiting process.