Technically, you're right, it doesn't. No voting or voting for a third party are indeed options, but it certainly implies (but, with a hat tip to Peter Sagal, does not beg) the question, "If I can't vote for Biden, what else am I supposed to do?"

The other option is Kamala. She can just step right in, all he has to do is say "I release my delegates and endorse my vice president."