(1)What "...reduction in traditional buckshot pellet diameters...", was made? Link please.
Go to the SAAMI website and you can download their book of shotgun standards (as well as a whole lot of other stuff).
The standard sizes have not
been reduced. 00 is still defined as 0.330" diameter. The way the manufacturers get away with calling their loads "00 Buckshot", while selling shot as small as 0.317" (or even smaller) is the tolerances
accepted by SAAMI.