I can only speculate that you're referring to ride alongs to which I responded:
Actually I think he was making reference to the tight angle kill from someone else's fight.
I watched the film and the truth is what happened was a fair and clinical kill. The duelling tradition Nath refers to is indeed a thing all duellers know about, but I do not believe it applies in this fight.
What happened was that one pilot made a decisively slower merge and got around in time to line up on the canopy of the other. The opponent pulled in harder and eventually comes to within about 15 degrees off head on, but by this time he has already taken an engine hit. Even in a friendly duel this shot will be taken more often than not. A few rounds squeezed out just to let the other guy know he is under pressure. The difference is that usually this shot will not connect or if it does, significant damage will not be recorded.
In the rare moments when it does produce a kill usually the shooter will say to his friend 'oh, that was a bit tight, sorry' to which the other will usually say 'nah, I didn't have a shot, it was fine.'
In this high pressure competition it is not right to assume that 'a bit tight' shots will not be taken, sometimes successfully.