Why do you think this exchange happened in a private meeting (rather than in an official letter) ? [Remember, Document B was published in the New York Times].

The reason why the exchange happened in a private meeting was because it was safer that way, it represented a better scenario than wihout all the pressure and vigilance. Then, the official letter would come after the resolution to calm everything down and reach a conclusion to the matter.

Explanation:

The matter in question was a very difficult one because it could have triggered the war, but the private meeting carried on as carefully as it could provide the right elements of discretion to make the Russian party there was no intention of creating conflict. Also, because the whole event was a misunderstanding and a misfortunate casualty. Therefore, the letter that came after was evidence of the great diplomatic job the U. S. government was promoting.