That Occam's razor thang works for me here.
The simplest reason why (and thusly by OR the most likely) is that Metro doesn't want Any hassles with a BYOD phone they switched over coming down on the Next Blacklist (with the BL date the day before the Metro activate) and risk having to tell the customer, sorry, you no longer have a working phone, click, buzzzzzz. The easiest way to do that is to make sure Every BYOD device is unlocked. That should if I understand things correctly, solve any potential black list problem.
Bruce in Ocala, Fl