Looking at the photos, it seems they cut the 8" round from a piece of 1.5" plate that wasn't. Why, is anyone's guess but photo #1 & #2 it seems that your calipers are placed by a start hole of a plasma/laser/waterjet cutting operation. Maybe it's just a dinged up piece of round. Without a photo showing the saw cut that's just a guess and .071" in plate not listed as precision fits mill tolerances today which run on the lean side of stated thickness. With that said, most cut to length supply houses don't use a measuring tape and rely on the cnc readout on the saw. It does seem to be a lot of effort on their part in an attempt to save .050"