FGD135: With the experience of being a radar controller for many years, and knowing the dangers that mis-identification can bring, it would be unthinkable of me to beleive in identification in any terms other than black or white.
Collins was a senior captain, widely experienced in being under radar control in many countries, and you will have some trouble convincing me he would have been influenced by the very brief flickering of the transponder light in the manner which Dozy Wannabe suggests.
Imho there was no room for any shade of grey in his (Collins) situation.