Very strange indeed !! last month you were asking for conclusive proof of F-16 shot down ... Am I right ?
Now you are talking about leaks ... GOD know these leaks are to save the LM from losing the F-16 race for IAF...
It suits you very well to ask for conclusive proof from Indians and believe leaks from Americans ? It suites your narrative very well ...
Americans also claimed the Saddam has Nukes !!
As I said many times before, no fighter is invincible. Given the right tactics, pilot skills and luck an older plane can shoot down a newer plane. So this is not totally surprising.
Thus, even granting for the sake of argument that IAF's Mig-21 did indeed shot down a PAF F-16, still the fact remains that whichever you look at it, the F-16 will still be the superior fighter versus Mig-21.
And regarding believability, well the IAF is in a fight to save its face against PAF so you should take all their claims with grains of salt. It does not help that the IAF seems to be incapable of showing further proof of downing F-16 than mere say-so. The same cannot be said of these 2 sources from US military who allegedly have access to PAF F-16s.