Ole Joe aint picking anyone. The DNC, Sanders, and The Squad are squabbling. When they agree they will tell Joe to read the statement and then go back to the basement.
You are exactly right, that Joe is not doing this pick.
But, it’s equally true that Joe is not even the candidate, in the conventional (or even any meaningful) sense.
This Chinese virus wasn’t released and national riots weren’t started so that Joe could be President.
If they're smart they'll put a mask on Joe and have a vocal impressionist read the statement. All Joe would have to do is pretend he's Charlie McCarthy (Candace Bergen's wooden brother); the mask would obviate the need to precisely sync his lips.