As the President of the most powerful country in the world, and as someone who has spoken to the CDC Director frequently, I can't imagine its even remotely possible for him not to know.
Furthermore, we also know Biden doesn't talk off the top of his head, he reads a teleprompter. The people writing what he says are likely quite competent mentally, so I would still consider it a lie in the end. Although, whether Biden even know where or when he is half the time, that's debatable for sure.