> It seems like you have equated "excel" with "must thrive under pressure"

Thriving and excelling are not that far apart :).

Thrive: grow or develop well Excel: be exceptionally good at or proficient in an activity

> It is not the single most important skill

Nobody said it was!

> everyone must be filtered on

It's a data point. Exam scores don't matter when you apply for a job, or do anything else in life.