From what little I know of it (and those more familiar please correct) the Reds will have briefed using information provided by the AIDU to the RAF. Considering the number of airfields worldwide that they cover, and the possible delays in the revision process, sometimes these things will slip through, particularly if the airfield in question was relatively small and not normally visited by the RAF.
Looking at the bigger picture, though....getting a frequency wrong vs. flying through a display featuring nine aircraft trailing smoke that I have seen in the past from over 20 miles away.....?
'Nuff said.