My point was this and only this: if that monastery is 2600 years old, and was always Buddhist from its beginning, then Buddhism came to Afghanistan before it even began -- because Buddhism itself is 100 years younger that the monastery.
It's only a minor point, I know, and I meant it as such.
Agreed. There is a dating issue in the article. OTOH, the Buddha’s birthday seems to me to have always been a rather hazy thing.