Biden is showing signs of decline, but the name-swapping thing was never (and still isn't) that. It's mental klutzery, nothing more. As the other person pointed out, it is /very/ common when two names are mentally-adjacent, to reach for the wrong one. My parents would call me by my brothers' names all the time, and I just did that with my own kids this morning.

Anyone who thinks that Biden got confused and thought he was in a press conference with Vladimir Putin (!!) is just spouting nonsense.