Hi Rejects. I can totally understand your confusion. I have no more insight into the Oxford process than you, but I do know that the tests are only one part of the process. For instance, in Chemistry, they dropped the admissions test because they tracked those with high scores through the degree and realised it was an indicator of nothing.
Thete is a website called 'WhatDoTheyKnow.' If you go on and type in your DS' course, you might well find people have made FOI requests over the years, eg. 'Please list all the tests scores and / or A-level predictions and / or interview scores for accepted and rejected candidates.' Even if they don't have his course, there will be requests for a similar course. You might well see that many students are being rejected with higher test scores than many who are accepted. Which makes you wonder why they bother with the test at all.
But anyway... he will almost certainly be able to request his interview scores. So he should do that first and foremost.
So.., this is C some years ago, but my DS was rejected. Also all A star predictions but, for his subject, they had done away with the admissions test (for the same reasons as described above - they realised it was a predictor if nothing). He was however, pooled (but at C, only about 1 in 6 are selected out of the pool).
He asked for feedback. They said that basically, what had let him down was his second interview score which averaged at a 6.9 (yes it was calculated to the decimal point)! They said that they did however, have sufficient confidence in his application to put it in the pool, and did not doubt he had the potential to do well at C and every year they inevitably have to turn down many very able applicants etc etc ... so they were sorry to hear he had not been taken out of the pool.
Anyway, as the months went on, he decided it was worth another shot (also he had applied in the hideous Covid year when Oxbridge had made significantly less offers overall across all subjects). He achieved quite a few things in Year 13 that strengthened his application, so this was why he felt it was worth a second shot. He was successful second time around and he knew his interviews has gone very well (in one they even said, "When you come here would you be interested in....")
If your DS' interview scores come back as hovering around a 7, this means 'possibly worth a place' (I have seen the form they use). In this case, and if there is anything he can do between now and Sept to strengthen his application, it may well be worth him having another shot if this means a lot to him (assuming he does achieve those four A stars which I'm sure he will).
Basically (particularly if reapplying from a selective school) - he has to think of it as "don't give them a reason to turn me down." So... they can't turn him down for his contextualised GCSE scores, from what you say. If he gets top A- levels, that's that box ticked. Then he needs something 'extra' to make his application stand out (hard to suggest anything without knowing his course). Then he needs to look again carefully at college choice. Maybe even look at applying to C if the course is also on offer there (I only say this as they don't reshuffle at the point of admission, so you can be more sure who will interview you and what will happen).
Bear in mind that if you apply post A-level, it's an unconditional offer. So no uncertainty for the rest of the year and they can even get ahead with reading, or work or travel and just grow up generally.
But for now, I would just get his interview scores. See how he feels then. I'm sorry he is in this situation with the other kids at the school and I do feel for him (and you). But really, it will work out - one way or the other. And if he doesn't decide to reapply, there is always the option of a Masters at Oxford. Give it time and breathe. He will work it out.