On my course at an ex poly, less than 4% of people got 1sts and roughly 30% got 2:1s. It was one of the better ex polys and there were people on the course who had reasonable A levels (c. 22 points), but who had gone there for reasons unrelated to entry requirements (e.g. wanting to stay close to their home town). These were the people who got firsts. They had a real talent for their chosen subject and worked extremely hard.
My brother does a similar course to mine at a top 5 uni. The teaching is far more in-depth, due to the capacity of the students to understand it, but that doesn't necessarily meant that the standard required in assessments also has to be dramatically higher. It could even be the case that while the exam questions may be fiendishly difficult compared to an ex poly exam on the same subject, a bunch of half-answers will gain you an A grade, whereas in the ex poly one, you would have to give full answers to easier questions. There are certainly ways to reconcile higher teaching standards with fair assessment standards.
Incidentally, I have seen some of the A-graded final year projects on their website and was not very impressed. A far larger proportion of students on my brother's course get 1sts. If the same proportion got 1sts/2:1s at both unis, that would certainly mean dramatically different assessment standards. Maybe they are not as different as old university students would like to believe.