Don’t see why the tyre being older than car registration is confusing. Obviously the tyre was made before the car.
It was the fact it's a Chinese ditchfinder so wouldn't have left the factory with it. Although I suppose it could have had a puncture in the first year or so & been fitted then. I just know when I've bought tyres they have never been more than a few months from the manufacture date. We put a set of 4 Goodyears on the wifes car & they have a date of week 40 odd 2019 for example.