Your call - though it's true. The bit about Bristol is probably independently verifiable. Their website will show you the grades required for maths now (for all I know it's higher than AAA now, since it was 2 years ago that he got his offer). Other websites exist that show the normal offers for...
In my personal experience it is definitely true, at least in STEM subjects. My son got an A* in Maths A level; he volunteered to take a scholarship paper I sat in 1975, aged 12 - he got 17%. He got an offer from Bristol Uni to read Maths there; the requirement was AAA. I got an offer to read...