The opaqueness is unique to USA and is thanks to "holistic reviews", which is a highly questionable practice.

Elite-College Admissions Were Built to Protect Privilege https://www.theatlantic.com/education/archive/2019/03/histor...

The new holistic admissions policy worked as intended, successfully suppressing Jewish admissions. https://www.economist.com/united-states/2018/06/23/a-lawsuit...

The 'holistic' admissions lie - The Daily Californian https://www.dailycal.org/2012/10/01/the-holistic-admissions-...

The False Promise of 'Holistic' College Admissions - The Atlantic https://www.theatlantic.com/education/archive/2013/12/the-fa...

Lifting the Veil on the Holistic Process at the University of California, Berkeley https://www.nytimes.com/2013/08/04/education/edlife/lifting-...