But how many people actually do, and how many technicians will actually look and say "hey, this tires 4years old already so you should pick out another set?" Having information available is useless if no one utilizes it.
It's just like with lugnuts, the technicians should properly torque them down and the customer should always check themselves before they start driving, but how many people actually do?
Obviously that is why it was mentioned. You tend not to need to mention things that everyone does anyway. However the important detail is ask about the date BEFORE buying the tires, before they've mounted them, even before you bother to go to the store if you can get them to check ahead of time before a potential commitment to buy if they're new enough.
Not quite the same with lug nuts because the average car owner doesn't own a torque wrench to check that while (hopefully) everyone has eyeballs to look at a date code to confirm the date the seller told them when they asked about it. Many shops do not let customers into the bays to play with their torque wrench to check that, something something liability of customer getting hurt in the shop area.
I just check the torque when I get home, to be sure some shop monkey didn't torque them till their impact wrench wouldn't go any tighter, to be sure they're at the right spec so there won't be any trouble removing them in the event of a roadside problem. I've often found them to be overtorqued but never loose... though I suppose it's possible.
I wouldn't hesitate to buy the same make and model major brand tires at Costco, Walmart, etc. as long as they're under 18 mos. old or priced low enough to offset the shorter anticipated lifespan. The whole binning quality to send to different retailers and wholesalers, I don't buy into that. A major manufacturer doesn't want to blemish their name, except you can sometimes find cheaper blemished tires, white lettering not quite perfect but so many these days have no white lettering nor whitewalls.
Plus, a tire that's defective will be a liability for the manufacturer. As far as using different rubber on the same make and model of tire, that makes no sense to have to set up a second manufacturing line to do that, would probably be more expensive than just using the same premium rubber for all of that model, and it would change the specs.