The point is to provide a meaningful metric schools can use to determine how likely a student is to succeed at their University, and how much success they are likely to achieve.
Bad or average cheaters are unlikely to find success. Maybe great cheaters are likely to find success.
It will just catch the dumbest and most people will cheat successfully. Just catching the most blarant and naive is stupid when the alternative of people being supervised in a physical room means there is next to no cheating at all.
Catching all cheaters is impossible for any reasonable amount of cash spent (remember all the possibilities people came up for that chess thing?) - which means they want to reduce cheating to a level that is acceptable.
Things they're not doing that could allow some high-level cheating:
That’s really all that’s required.