To my understanding the 109 is definitely very much slower than RL at altitudes above 5500m, at 7000m by 30-40 kph. That is a huge discrepancy. As far as I can read kyrillic letters (I am learning Russian a little bit) the blue curve shows RLE values (so flight tests by the British), the purple one says something like "igra forsash" (= game XYZ?) and the grey "igra bez forsasha" (= game ....?)

My guess is that the purple line is post patch the grey pre patch. the purple line is following the grey line (just beneath it) from alt 5200m.