Lemain,
You say "But it was speculation that the pilot might have been under qualified or not medically fit that made the investigating team check that out". I disagree; qualifications and medical fitness are de facto potential causal factors that have to be checked in any such accident. They did not just check these because there was speculation about these being potential causes in this case.
You also say "If the radar track is, as you say, relevant to the inquiry then surely the accuracy of that track is relevant?" The radar track was relevant but within the uses for it (building awareness of the display pattern) then numerical accuracy was not. There are no conclusions, causal or contributory factors in the report that are affected by numerical accuracy data for the radar track.