Not something I'd do on purpose!
Reloaders worry about changing component brands from shotshell manual printed recipes and raising pressures too high.
Here you have the entire front half of the (12ga)
hull being squeezed down from .800" to .729" through the forcing cone as SWChad points out.
That .800" dia bundle of hull, wad and shot is sized right about 1/2 way between a 10ga and an 8ga bore diameter.
Most all over the counter ammo is loaded at or near SAAMI limits (to make sure they operate in all firearms), spiking the pressure more isn't something I'd be looking for.
Now there's probably somebody around that has 'proof' that it doesn't,,but I'll stick with the regular loads, thanks.
410 shotshells are noted to do this (separate) when loaded way too many times,,which tends to happen with the expensive little things.