So in your 75 years, you've measured every new tire the same way and have never seen this? Or might this be one of the few tires you've even really measured. And you are doing it wrong as far as measuring height. The BSD of a tire is measured to the shelf the bead sits on, not the outer top edge of the rim.

The Mavic's I just measured have about 5mm from the edge to the bead seat. So there probably is enough distance to make that tire come out as being 28mm tall. Tire size is only width and BSD. Though it is generally acceptable that the width of a bicycle tire height will add the same amount of distance to the BSD so it's overall diameter and circumference can be figured. But it happens on both sides of the rim, so multiply by 2.

Still are you certain the tire is seated evenly all the way around the rim. I've never used that brand, but many of the other's I use the witness line sits further away from the edge of the rim.

And despite any of this, I fail to understand why 2 or 3 mm matters for a bicycle tire size. It won't make that much noticeable difference to my ride or performance. And it won't be on my bike that long anyway before it's time for another.