Thanks for the reply's. For some reason the tag tires are different that the rest and...for unknown reasons, the PO used on/off road extra heavy duty tires designed for concrete trucks, and the like. As for the wear pattern, tough to tell with only 10K mile on them even though they're 6 yo as they have a very deep tread so basically they look like new.
About using the tag tires as a spare, tough to see how that would work since I can't drive more than ~15 mph with the tag up and I would still have to buy a new tire.
Still, something to consider and these tires in this service might just last for many years without issue.