Confused about AQA GCSE Physics grade boundaries...?

The UMS grade boundaries for GCSE never change - 90% or more for an A8, 80-90 for an A, 70-80 for a B etc, However, if you have fixed grade boundaries you can't adjust for one exam season's paper being harder than the next so they make the adjustment when converting from raw marks to UMS marks. Your 72% would have been a UMS score, the grade boundaries you found on the AQA website were showing you the raw grade boundaries for a particular paper in January 2011, and obviously it must have been a really hard paper.