I am 99% sure you are correct. Square is new. Not 2015.
Caveat: 1% chance that I’m wrong, I always put a disclaimer on statements like these.
Either way, the new square tins are good and there is nothing wrong with less aged Penzance, I sometimes prefer the new to the aged.
Those are the "New" tins. Not consignment.
I have tins dating back 11 years. You can see below, the square tins started just recently vs the old rectangular tins. The older 8 oz bags are white vs the newer gold. Same for Stonehaven.
The square tins began importation into the USA in 2017. I have not noticed any difference in the cut of the Penzance, but, when I got my first square tin of Stonehaven and compared it to the leaf coming from a recent production bag, the flakes were a little thicker cut in the new square tins.