No i don't think its a good ideal
Yes sir, that could be the reason - another reason is our location. Here in Iowa, especially in the winter, folks wear a lot of layers of clothing and that too may be a factor. I know I carry different ammo in the winter than I do in the summer (also when I'm in Arizona instead of Iowa).For a LEO it may be more important, they have to shoot thru car windows at times, we as civies, need that bullet to stop when it hits what we are aiming at. I would think that is the reason for the staggering of ammo.
I've heard of that for as long as I can remember, but I don't do it.I know a few LEO's that actually stagger bullets FMJ,JHP,FMJ,JHP etc.