Does anyone remember when the new $5 bills with Carney's signature were issued? For the first 5 or 6 years only 3 were known. Then, all of a sudden, here in Vancouver, I started to get new Carney notes from my bank- plain uncirculated, available in "large" numbers. The belief is that some of the new bills were printed and then put somewhere for storage. The second signature notes were put on them, and the pile did not get worked through for several years.
Please note from the forum notes that the serial number starting points for the new Wilkins-Macklem notes were available in 2020. Some of the serial numbers starting points for the Lane-Macklem notes are already being talked about. The unreasonable high numbers could be products of this type of process, with later printings covering up earlier issues, and sometimes new ones being released earlier than most of the earlier printings.