Hey Rick,
Thanks for straightening that out. So why the use of FMJ in the military then? ...or is that also not the case in terms of projectiles?
Well, all kinds of reasons.
You can start out with various international treaties on how we will wage war. However, if you want to add to your confusion, some of our ammunition is hollowpoint - but it doesn't violate the laws of war because the hollowpoint is intended for precision accuracy and stability over long ranges, not designed with intent to expand.
Then you can consider that we aren't just using bullets to shoot deer, but to shoot through building walls, vehicles, heavy brush, etc. And a bullet tough enough to hit dirt, pavement, cement, etc and then keep on travelling around in the enemy's general vicinity at high rates of speed is met with general approval as well. Bullets hitting bad guys while bouncing around in "to whom it may concern" mode is not a bad thing. Penetration of cover is pretty important, which is why a lot of infantry guys get a giggle when they watch movies of gunfights with the combatants hiding behind walls in buildings and ducking out to shoot at each other...
Then you can think about the beating bullet noses take feeding through automatic weapons i.e. the C9 and C6.
Finally, the idea that FMJ just drills neat pinholes through people isn't based in any reality. You don't have to stumble very far searching the internet to find ongoing discussions (arguments?) over the effects of bullet yaw, tumble, etc once having hit somebody. Not a few ball rounds are designed at least partially with the intent they will become unstable once hitting somebody. That isn't as significant with pistol calibers, but we don't do much fighting in combat with pistols anymore, and a lot of those pistol calibers get fired out of submachine guns in bursts at the bad guys - usually by specially trained units at kissing close ranges.
As far as some police agencies opting to go back to the 9mm, I doubt that much is being lost or gained as far as performance in stopping a threat. A more controllable round (when the reality is that very few departments fund regular range sessions for their members and never have) may have been trialed and found to provide better scores during range testing. But as far as returning to the 9mm (or 38 Spl if you want to imagine further), the bullets available today are not the bullets law enforcement had available even 10 years ago, never mind 20 or 30 years. I believe it would be quite sensible for any department to be far more focused on what handgun/caliber would result in a higher percentage of effective center of mass hits for all members of their force, than joining the very popular internet sport of dropping your guts over what caliber is superior to what. You know... when you get tired of the "which oil is best for my motorcycle" and "30-06 versus .270" arguments. Okay, maybe I'm dating myself with that last example.