as Tod has explained here, its widely regarded as a visa. I've never heard it called a permit, and as it acts as a visa would, I really dont care about the semantics of it, even in capital letters. Immigration refer to it as a visa, it gives me leave to stay as a visa would, everyone calls it a visa, thats good enough for me.
seems im repeating what Tod is also saying here. The non O Visa is a 3 month visa: your retirement visa ( so called) is a 12 month extension of that visa.
Reporting is a separate issue to when your Visa expires and is only ever a 90 day sequence. The date will be in the paper attached to the last page in your passport.