This video gets off to a slow start, lot of technical stuff about smokeless vs. black powder, but when he shows the difference in actual firing guns it's pretty clear that the video just doesn't have the quality or stability to draw this conclusion from. Comments also discuss how much easier cleaning and maintaining a gun is when you only use smokeless powder, so I would assume anyone who's job and life depends on the gun remaining reliable for a long time would favor it.
More importantly... I'm just trying to figure this one out. Who benefits from this, who would do it, and why?
The officer and the department both face massive criminal and civil liabilities due to a shooting that neither denies happened and neither denies was intentional (but both deny was unjustified). They gain nothing and stand only to lose greatly. This was a police shooting and not a civilian with a gun, so there's no way to use it to justify gun control legislation. If the officer and department escape without penalty, nothing changes because police are killing several hundred people a year in the US without penalty. If they are hit with the full liabilities they face, nothing changes anyway because police are killing several hundred people a year in the US without penalty and this does nothing for the families of Milton Hall, Charles Ray, Brian Vander Lee, Dennis Gaydos, etc etc etc.
"They" stands only to lose here, nobody else stands to gain except for one family who has to bury a loved one first, and "they" are the only ones who could have done it anyway