Interesting. Perhaps you do buck the trend, but all trends lead to someone like you (high SAT scores) easily achieving a high grade at A Leve maths. There is a big jump from GCSE maths to A Level maths, but not quite as large as you’re suggeting. I think the jump from AS to A2 is bigger, personally. They do a further maths GCSE these days which kind of bridges that gap between normal GCSE and A Level. That would have probably helped. Students who take their GCSE a year early tend to do the further maths GCSE in year 11 which would have probably benefited you rather than doing the AS in year 11.
I found statistics to be hideously boring, but pretty easy. Got a B on that module I think. The “pure” stuff was by far my favourite part about it.
I’m a bit different to you. I loved maths in primary school. And then I hated it for the first few years of high school - found it boring and couldn’t see the relevance of it. I was always top set, but my test results were continuously towards the bottom of the class. Then I got to year 10 and something changed. For whatever reason it suddenly started really interesting me and I decided I was going to do well in my gcse. Ended up in the top 3 of my class. My real interest in the subject began at A Level - there were still too many topics at gcse that to me felt like basic numeracy skills than actual maths.