Maybe they are looking for aptitude rather than experience and grades? One kid at DDs primary started playing violin in year 5 and by Xmas of year 6 was given music scholarship - progress had been rapid! Still didn't have the grades bur far more potential than those who had played for years.
Yes of course, the Bentley test is designed exactly to do this and it is an admirable intention to try and equalize the results between inexperienced musicians and grade 4/5 achievers.
However I still find it hard to understand how someone can get to grade 4/5 with no or limited aptitude which is what failing the Bentley test would seem to indicate.
Maybe a better measure would be to audition all applicants and use a combination of the results although that would increase the workload on the testers.