I think when courses are very competitive, you need predicted grades in excess of the standard offer, and impressive GCSEs too.
You might be right that they are filtering on A Level subjects and preferring candidates with traditional subjects and possibly prioritising those with A Levels over other qualifications such as Btec.
I also think people forget just how many candidates have all A star predictions and all or almost all GCSEs at 9/8. In some schools or colleges, having an A star prediction puts you in the top few of your school, as does a couple of 9s at GCSE, but there are lots of selective schools which have the majority of students with predictions of at least one A star and lots with all 3 or 4, plus huge swathes with all 8/9 at GCSE. For some courses at some places, it is insanely competitive and unless you qualify for a contextual offer, you have to be absolutely stellar.
It’s really tough, especially if you’re in a school or college which is very conservative with its predictions. In the end, those with those very high predictions are getting the standard offer which they might well achieve even if they don’t get their predicteds. Those who are simply predicted the standard offer and actually achieve the same grades as the person with the higher predicteds is less likely to be going, as they simply don’t get the offer.
That said, they say 80% of predicted grades are wrong, with most being too generous anyway….and that’s a widespread thing. Usually schools and colleges do know from past experience the kind of grades their students of different ability types get, but with Covid and return to so-called normal grades has made that more tricky.
It is disappointing for a school or college if the students they think are really strong all don’t get iffers for a particular course. I suppose the question is whether they are super strong and their predicted grades are too conservative and holding them back, or if they are just strong, but not super strong and not quite competitive enough with the many who are top-notch academically.