Fair comment ... one group from one batch from one shooter isn't conclusive ( Si's ). Your results seemed to support the theory.
I still think though that the ultimate test in both yours and Simon's case has been a bloke shooting the pellets to check the groups ... outside in wind. So we are always guessing as to whether the groups and anomalies are due to the pellets or the wind or the shooter.
It would have to be done with readings at the muzzle ... maybe at a mid point ... and at the destination ... and indoors with no wind ... and with some sort of vice/clamp and remote trigger to remove shooter error.