I read that article where it says #1 buck is the best, and wonder if things have changed all that much since it was written in 1998?
I think the shotgun in general is so effective that a wide variety of ammo can be used in it and still stop an attack.
You don't have to be optimal with a shotgun blast, certainly you don't have to be perfect.
With handguns, we saw the 9mm Silvertip, a particular design in a particular caliber, pushed to center stage in the analysis of the 1986 Miami shootout. THe end result is that hundreds and hundreds of police departments eventually migrated to using the .40 S&W. Whether that was political theater, right, wrong, good, bad or whatever, my point is we saw an event that changed what kind of ammunition / caliber handgun was chosen by a lot of people.
I think two things mitigate against anything like that happening with shotgun ammo:
1) There has been a proliferation of 5.56 rifles and carbines in LEAs and a lot of what the shotgun platform used to do is now being done with 5.56
2) LEA and military generally use 00 Buck and they don't play around the edges of what's possibly ineffective against humans ie: birdshot, or #4 Buck and 00 Buck is effective enough that you probably will not see a catastrophic incident where a major LEA comes to the conclusion that using #1 Buck would have made a difference over 00 Buck.
One parallel I do see in this debate - when people make over penetration the priority and over riding concern - you can get into a situation where the projectiles simply do not penetrate deeply enough to disrupt vital tissue.
The Silvertip didn't "fail" in the 1986 Miami shootout, it performed as it was designed to perform. The 9mm caliber didn't fail in the Miami shootout - there were plenty of different bullet design at the time - including simple FMJ which, if it had been used would most likely have punctured Platt's heart and ended the conflict before he could have killed two FBI agents.
If law enforcement made over penetration their main concern with their shotgun platform, and started issuing birdshot to all their officers, could something similar happen ? I think it could, but I don't think LEAs will ever switch from 00 Buck.
00 Buck may not be optimal but it works, and unless there is some catastrophic failure with it - law enforecment will never move off that loading.