I find your analysis fundamentally flawed, icebeing for a number of reasons including:
As an admission tutor at an RG university you do have the ability to make contextual offers if you feel grades are over or under predicted in one group of applicants - in many courses the stated admissions criteria shows a range;
Your argument is based on the assumption that independent schools DO over predict - and several people on here, myself included, have illustrated that their schools use only the AS grades as a predictor and do not inflate - so there is no cross sector pattern;
Your argument that a male makes stand more chance of getting on a physics course flies completely in the face of the Women in Science initiative which is moving the dial on that statistic - which is in any way majorly affected by the number of applicants in the group, rather than differential offers within the group;
And it ignores the fact that many students in independent schools are already predicted to over achieve the offers made to them ( eg achieving A*AA against an AAB offer) whereas the average achievement in state schools is lower, so students arriving from state school are more likely to have hit the offer spot on. So that's why they have lower average grades - not because it was harder to get an offer in the first place.
But is is very hard to generalise about 24 universities offering thousands of courses to tens of thousands of students, so anybody else's take on the situation is just as likely to be valid as mine. And there's a whole industry out there trying to analyse all of these things one way or another and I just don't accept that it's clear cut.