I do hope this is not the case. However, it is true that if the majority of the cohort is unsuccessful, then they will drop the grade boundaries from the last years. They usually do this for exam by 1 or 2 marks, so not making much of a difference if you secure a good grade. It doesn't seem to effect coursework marking as it usually stays the same.
I know my A2 Philosophy exam went awful, the A2 Ethics went a whole lot better. But because Philosophy is harder, their grade boundaries are usually lower and Ethics is higher. So I don't know how things like that work where it's not at an even standpoint.
But I'm just hoping I get the grades I need to get into my firm choice uni!