As regards use in semi-autos, most modern SA shotguns are gas operated. Now if one studies the pressure curves of equivelent loads using different powders it will generally be noted the "Low Pressure" loads actually have a higher pressure down where the gas port is. I think what comes into play mostly is at the "Low End" of the shot charge wt. When I began shooting a shotgun back in the '50s min factory loads in 12, 16 & 20 were 3-1; 2½-1 & 2¼-7/8 respectivly. Recoil operated autos when set for light loads would operate these guns reliably. With the introduction & proliferation of Gas guns these loads in 12 & 20 were increased to 3¼-1 & 2½-7/8 with the 16 remaining unchanged, Why?? No-One was building gas 16s!! "My Theory" is this increase in Dram Equiv was made in order to stay with a fast powder which was running out of steam prior to passing the gas port. No doubt the same ballistics could have been maintained by a switch to a slower powder which would have maintained adequate pressure at the port, but this would have required a larger increase in the wt of powder charge than a simple increase in the fast powder charge. Likely these older loads were operating enough below SAAMI max the increase could be made. These older loads were incidently much more comfortable shooting in light wt field guns than their modern equivelents, the price we double gun lovers have had to "Pay" for the "Reduced Recoil" of the gas guns.
Bottom line is it was all "Economics", not that a load using slower powders could not be made to operate a gas gun.
