No, that is simply not how it happened. He didn’t announce it, Faye Dunaway did.
If you watch the clip he is clearly confused about what to do and doesn’t want to read from the (wrong) card in his hand. That is because he had somehow been given a duplicate of the Best Actress card with “Emma Stone, La La Land” printed on it. He clearly does not know what to do, and Faye Dunaway is urging him to make the announcement. He shows her the card, she sees “La La Land” and announces that. The card was not printed with the Best Picture info.
The clip of the snafu is linked in this article:
He may have Alzheimer’s, but he has some lucid moments. Blonde is permament