Probably related to the recent bank fears in the US and higher than normal demand for cash if it was a recent withdrawal. Or somewhere a inventory was taken and older cash was moved to the front for distribution.

You know how something just gets left at the back of the cubbard/drawer because you keep restocking at home? That is probably what this is. Somewhere at some cash depo (bank or otherwise in the distribution system for ATMs) these were sitting "at the back" in the inventory and higher than usual ATM witdrawals for example made them finally enter circulation.