"Determining proper allocation between wages and distributions of S Corp shareholders is not an uncommon issue"

What you have not told us is if there also was reasonable compensation all year. If there is already reasonable payroll, then the Bonus concept should be fine. The date the funds were given might be treated as lending, and the bonus check is treated as, "We changed our mind, and will forgive the loan."

But, if the taking is routine, such as when someone takes both payroll and distribution at the same time, and the distribution is routine and ongoing, that is a bit harder to justify as "lending." It looks a lot more like attempting to avoid payroll treatment.