I think it's possible he was reviewing documents for potential release or even was looking because he found recent revisionism irritating and he found the sheer absurdity all the more striking based on information he observed therein.

I neither like nor trust Putin generally, but he frequently tells the truth about his enemies because that is enough to condemn them*

*aside from the "The West is sending homosexual ideology here to make Russia weak" type stuff, obviously that is bullshit and should be called out.