Well, it may be similar in diameter and weight to a buckshot pellet, but it is not a ball, and it is spinning from the rifling. It has a deep hollow-point, but is solid in the back, so it probably does perform much better than a pellet in terms of flight pattern. Also, theoretically you might be right about the heavier bullets shooting flatter at long distances, but what distance? The 50 grain is obviously initially flatter, because of the velocity, so it might not be for a very long distance that the average speed would begin to favor the 115 grain. The 50 grain is probably still moving well over 1,000 fps at 200 yards, meaning it's surely flatter at that distance than a 115 grain starting 1,000 fps slower. That 2,000 fps claim has been confirmed by a few chrono's on the web, and that's from a handgun. Perhaps it comes out of a rifle closer to 2200 fps?
I would agree that lethality at 200 yards is probably not great, and wind probably would affect it a lot. However, I wasn't expecting good performance at 75 yards either, and it was excellent, so who knows for sure until we try? I'll report back in a couple months when I actually try it at 100 and 200. I'm really surprised nobody else on the internet has spoken of this, considering that 9mm carbines are fairly popular.
btw, I didn't notice any difference in flash, but I wasn't looking for it either. The sound was different, and the recoil seemed lighter.