Replacement TT tires, Date code

Yes.
I would accept new tires 6 months old or less. Also not stacked flat in a warehouse for long periods. I'm paying for new tires so I expect new tires w/i reason.
I've had tire dealers roll a tire out for me to look at the tread design that were mashed from hard telling how many tires stacked on it.

My understanding is yes... they are aging as they sit. When I put new tires on my travel trailer, they were only 3 weeks old. I put new sneakers on my truck last November, they were all about 3 months old.

I dealt with a local tire company in my hometown.

Yep thats why they were cheap on eBay :S

I ordered from Discount Tire Direct and received tires 14 months old.(even after I added a note not to send tires more than 6 months old) I called to complain and asked for either fresher tires or a return label. They supposedly checked all their wharehouses and had non that were newer. After I explained that I had lost a year of use they gave me a $50 credit towards my next purchase and refunded me an amount that made the tires a 3 year price rather than a 4 year price. Call and complain. It's worth a try.

ASK before ordering what's the date code on the tires. If they avoid the question, find another seller.

I really doubt that you have lost 2 years of use, but you have lost some because they weren’t ever used. Waxes in the tires migrate from inside to the outside with use to prevent drying out.
I would complain to the seller that you didn’t get “new” tires. See what they say.
Stories abound here how so and so got 10 years from a set of China Bombs, while someone else only got 2 years and on and on.