I'll tell you what doesn't make sense...this ridiculous misinformation that keeps getting spread about tire age on forums. If I still owned a tire store instead of being retired I would love it! At the current rate of travel, people on here will be advocating yearly tire replacements sometime in the near future!
The 5-6 year window is a myth to begin with. No less than Michelin, probably the worlds most trusted tire company, says 5-6 years is when tires should have a yearly INSPECTION. They state tires can last ten years but should be inspected for tread separation, bulges, etc annually after five years.
The reason tires deteriorate is because of UV exposure and exposure to the elements while in use. Tires stored in a warehouse certainly are not aging at the same rate as tires traveling down the road. Tires stored on a vehicle parked in a garage are not aging at the same rate as those sitting uncovered in a wide open parking lot.
Tires fail most often because they have been damaged while in use or because they are run at improper air pressures for their use. There is simply no reason to worry about a few months old new tire being installed as the aging process is no where equivalent to one in use. There are a ton of logistical reasons why tires are not immediate production line to mounting on a vehicle. By the same token there are a ton of reasons tire aging is not linear from the production line to the end of usability. People would be much better served to be concerned about tracking tire air pressures, weight load, and annual inspection instead of these amateur "the sky is falling predictions" you find on forums such as these.