Scroggs and WWW have explained it very well. Academic qualifications are no guarantee to success in aviation, particularly on a scholarship scheme. In many ways it is the indeterminates that count and that is why most companies employ a peer-interview process either solely or in addition to the profiled objectivity that comes from psychometric and other focused testing techniques.
The mere fact the BA and other companies employ line pilots as interviewers indicates the importance they place on that element of the program. The fact they have that element in the program means it is not quantifiable by normal measures. Therefore, merely because someone ticks all the academic boxes, and even may have a great deal of enthusiasm, that in no way guarantees they possess the intangible qualities; intangible to objective measurement.
It is something that frustrates the psychologists who design the tests for pilots, that they can't nail it 100%. The fact they can't is why most of us are here.