Nervousmom, you need to be a little cautious here. The cut off scores on offers day are based on information that is available to the school/council/FO and no-one else. They work out the cut off score, based on PAN, numbers of applications, scores achieved, numbers of PP places needed, numbers of expected rejections etc etc...a whole host of things that we laypersons can only guess at year on year.
As the rank scores in Warwickshire are consistent markers year after year, so the cut off scores for B'ham are their consistent markers, year after year.
Anything that happens after National Offers Day, from the waiting list is subject to change and variables too many to mention - and could, frankly, be described as "lucky". You are "lucky" if you get offered a place from the waiting list, or "unlucky" if you don't because it is so up in the air.
Someone may have got in from the waiting list in the December of Y7, with a pretty low score, but quoting that one individual as being the "last score in" isn't really a realistic picture. Whereas, the cut off score on offers day, helps give an indication of how likely a child's score would get offered a place, the following year.
Certainly, in an area like Birmingham where there are 6 choices on the CAF, a better explanation to parents that, if they are within touching distance of the advertised cut off point, and they really want that school, then it is worth putting it on their CAF and taking a punt, would be helpful!