"Inspected by Postal Supervisor"

When I was preparing to move, I arranged to have Canada Post forward my mail to the new address, just in case I forgot any address change. Shortly after I moved in, I got some mail at my new address with yellow forwarding stickers on it, so that made me feel reassured. But just before I returned the keys to my old apartment (i.e. over a week after the date when my mail forwarding was to start) I checked my old mailbox just in case, and found some very important letters in there. So I sent an email to Canada Post explaining the problem, emphasizing how serious the consequences would have been if I hadn't gotten these letters, and imploring them to make sure the forwarding went smoothly in the future. There was a brief email exchange where I clarified certain particulars (I hadn't known what information they needed at first), and then the next morning, while I was in the shower, someone from Canada Post called and left me a voicemail saying that in addition to looking into my forwarding request and making sure everything was good, they were having the carrier who delivered to my old address keep a lookout for letters with my name on them and physically hand them to the carrier at my current address if they find any (because apparently all the mail is given to the carriers at the same physical location). So I was happy with all that.

So today I got another very important letter, addressed to and delivered to my new address and marked "do not forward" by the original sender. And someone wrote on it in pen "inspected by Postal Supervisor", with today's date and some illegible initials.

I wonder if that is because of this mail forwarding problem, or if it's a completely unrelated thing?