For top courses, it may well be that fairly oblique messages are sent out about needing to have a good academic record. These messages won't usually identify specific numbers of GCSEs at specific grades, because they wish to maintain some flexibility, which is right.
However, to suggest all candidates have an equal chance of an offer or meeting their offer is just daft. It can clearly be seen for the most competitive courses that those who receive offers are those with the higher GCSEs. They have high percentages of A and almost or all A/A. This will be across whatever number of subjects they took - and it won't really matter if that was 8 or 13. It is better to have fewer with top grades than loads with a bigger spread of grades. So what about this scrutinising of a lower GCSE in Drama for example? Well, if there's a B in drama amongst a set of grades which is otherwise A/A it isn't likely to make a difference unles said dramanis the course applied for. But to suggest that for a competitive course like medicine or economics, at a highly selective uni like Oxbridge or Durham, the candidate with 6Bs and 2As at GCSE is as likely to get an offer as someone who had 7A and 1A is just daft. They might both be predicted the same A Level grades - that happens! But Unis don't just look atbtheboredicitions, because clearly the GCSEs give annindicationnof how likely the student is to achieve those predictions.
Take a look at the WHICH UNIVERSITY advice pages. They point out how GCSES usually correlate to A Level grades. I have also seen information which discusses predicted grades and the liklihood o meeting them or missing them - 2/3 of students were 2 grades short of their AAB predictions - for those with an average GCSE profile of A/B this figures was far higher than for those with an average profile of A*/A - hardly surprising is it!
Often the biggest hurdle these days is to get the offer. When results day comes, loads miss their offered grades, but with 1, sometimes 2 and even 3 or 4 grades difference across the offer, theyvarevstill accepted into the course. Unis want to fill up and Clearing is an uncertain place for them, so they'd often rather accept slightly lower grades,min owing the candidate wants to come to them and they can fill a place. So getting the offer comes down to having a good set of GCSEs and doing well enough in the L6th to get the predictions. Of course, for Oxbrdige, the internal exams they set are also vital in differentiating candidates. And students then need to not bomb out in the A Levels themselves, but for a good number of RG Unis, actually if they get a grade or 2 less, they will still be in. I have known this in popular course like medicine too. But in the example of medicine used upthread, without the required GCSEs used in the sift, there will be no offer at all.
It depends which uni and which course you are talking about, there will be lots of good Unis with slightly less competitive courses who will give offers to those with less fantastic GCSEs. They know that those students probably won't hit their ABB or whatever it is offer, but they expect to take them anyway. It's knowing where will be more rigorous and expect more to give an offer and for which courses. Schools which tell students 'any degree is as good as a degree from anywhere' or 'Unis don't look at GCSES only A Level predictions' or 'go on, have a go with those 8Cs if you really want to do medicine' or 'don't apply for Oxbridge because you won't take in/people from our schools never oo' don't do their students many favours really.
Students do need to be told what is realistic with their academic profile and encouraged to aim high within what is realistic.
If in doubt, email admissions tutors. Ask very precise questions about the GCSE profile of students they have made offers to in the last few years. This can be more revealing than what is shown in the prospectus. Some prospectus' say a minimum requirement and actually offers are made to candidates with those minimum requirements, but for others due to the no of applications, only those who far exceed that requirement actually get offers.