How do you know that there weren't people out there rejected from college courses when they would have been accepted in previous years?
Most courses fill target numbers, and they do that by progressively opening up the window until the course is full.
If there is a sudden burst of grade deflation, as happened at A Level maths a few years ago, several things happen. Firstly, you start accepting your firms even if they didn't make their offer. Secondly, you start accepting your insurance offers even if they didn't make their offer (there are reason, which I can't offhand recall, why that is harder to do in the process). Thirdly, you go into clearing. There was a problem a few years ago where the RG universities under-recruited because going into clearing was seen as the mark of Cain, and no-one was willing to blink first. No-one is ever going there again, given the financial devastation it caused, and now pretty well everywhere other than Oxbridge, UCL and Imperial announces up front that they will clear.
So if there were system-wide drop in grades by a whole grade in every subject, there would be some turbulence on Wednesday evening and some exciting phone calls on Thursday morning, but matters would settle very quickly.
Or are you suggesting that the entire college entrance process ground to a halt in 1989 because no-one understood these new-fangled GCSEs? That university admission stopped dead in 1987, and again in 2000 because of the substantial changes in A Level grading?
Alternatively, if your contention is that small numbers being inconvenienced for a few days is unacceptable, what's your answer? That grading has to remain directly comparable by published norms from year to year? How?
One way we can do that is going back to norm-referenced grades, which we all know are simplistic nonsense. Look up what proportion of the population got School Certificate Matriculation in 1922 and fix GCSE A at that level, thus making qualifications "comparable" between children and their great grandparents.
Alternatively, we have to keep syllabuses the same indefinitely and mark against fixed criteria. That will see long term grade inflation as teaching improves (it's immeasurably better than a generation ago) and more children are raised in graduate households because of improving takeup amongst their parents' generation (which is what has happened to GCSE).