We've seen from the videos of the pilots that the flares scintillate as we expect.If your graph was accurate, the flare ought to be reddish, from the sunlight passing through a lot of atmosphere.
Does the angle at the center of the Earth correspond to the actual positions of observer and identified satellites?
What are you basing your 90⁰ sighting angle on? (perfect observer line vs. radius)
I think it is possible that the normal vector of whatever surface is reflecting the sun on the satellite may not be aligned with the center of the Earth, i.e. it might be tilted slightly north or south. Can we determine this from the data?