"Surface treatments" (as Armorall, Son of a Gun, etc.) are just that "surface treatments" to protect against ozone affects. No more, no less.
Dry rot happens well under the surface, with time and age. The tires can look pristine on the outside and be deteriorated internally.
Tires which are aged-out of use, but still on the car, CAN still drive ok and such, but ONE evasive maneuver or chuck-hole will be enough to de-bond the internals from each other. Usually not, from my experience, a "blow-out", just a loss of air and then a flat. Prior to that, they will hold air and perform as normal, in easy driving.
Just like an older car with Fingerhut (or similar) fitted clear plastic seat covers to protect the factory seat covers. They will look nice under that plastic, but be dry-rotted and fail quickly once those plastic covers are removed.
If not protected, upholstery fabric "dry rot" happens in plain open sight. As the foam underneath gets harder, too.
When tires would normally need to be replaced after 30K miles, we didn't hear about tire dry rot unless it was a very old and low mileage vehicle.
CBODY67