Hoo-boy; gongs are a sensitive topic. In Collishaw's case, his 6 victories on the date in question only involved one assessed as destroyed; the other 5 were OOCs. Note that those RFC/RAF pilots with 5-6 destroyed in one day did not receive the VC, so Collie's situation is not unique.
As for
EVR's Distinguished Service Cross (2nd to the MOH), it was basically an I-was-there gong. He had TEN of 'em by the time the shootin' match ended, as there weren't lesser awards to be presented. In WW II those actions (assuming they resulted in e/a assessed as destroyed rather than OOC or driven east) would have brought Air Medals or DFCs. I believe that the Silver Star was awarded after WW I to most of those troops whose DSC nominations were denied.
The late Marion Carl, marine ace and by-god warrior, said that major awards should be held until after the war in order to present them in a more even-handed fashion. Trouble is, military decorations are essentially stepping stones for careerists as well as morale builders for civilians. Therefore, most gongs are political and immune to systematic fairness or logic. (A former White House aide once told me that Lyndon Bastard Johnson used to say, "Trot me out a hero, son. I wanna make a speech.")