Why does the fact that they were previously acquainted affect the story? In fact, when I first read the story I assumed that R’ Gustman knew who R’ Aharon was. And the theory about R” Aharon Kotler seems like grasping at straws. First of all who was the milkman? Second of all, there is no particular reason why a story about R’ Aharon Kotler talking about a milkman who knew Shas would somehow evolve into R’ Aharon Lichtenstein volunteering as a milkman, and even more so with the whole rest of the story.
Good points.
Considering it again, I actually think the story makes more sense in the world where they did know one another.
It explains how Rav Aharon got involved in the discussion. I don’t imagine that the time it takes to drop off milk is long enough to overhear their entire question, and more, don’t you think Rav Gustman and his chavrusah would have said “hello how do you do” to the milkman instead of ignoring him and continuing their conversation? But if Rav Gustman knew Rav Aharon, he would have deliberately called him over and brought him into the conversation.
And then the comment that “the milkmen here are bekiim” would have been in jest, since he would have known that Rav Aharon wasn’t an ordinary milkman.
So if that’s the only kasha, I’m still believing the story.