Well, I can now confidently state that the Jan 15, 2021 date for the $600 per person second stimulus checks to be received is irrelevant. Today, Feb 4, a client called to let me know they received their check in the mail. This was a retiree, whose first stimulus payment (last year) was direct-deposited to their bank account.
So now we know that there will likely be plenty of confusion over whether to claim the second stimulus payment on the 2020 tax return, especially for early filers.