A whole bunch of things. Basically, pistol calibers don't have the energy required to cause remote wounds, so bullet shape is somewhat irrelevant in terms of what kinds of wounds the bullet inflicts on living tissue. Bigger bullets don't really make bigger holes because living tissue acts like water; it gets out of the way, then collapses back in on itself. A number of medically trained researchers have stated that they can't tell the difference between common calibers or bullet types simply from examining a wound channel. This has gotten somewhat better with hollow points that open up into petals, as opposed to the old ones that just "mushroom," but it's still a pretty small gain.
The main thing is that modern hollow points are misunderstood. The purpose is not to inflict larger wounds, but to limit penetration in living tissue, while maximizing penetration through hard materials like bone, window glass, etc. The ideal hollow point would penetrate as far as FMJ in non hydraulic mediums, yet only penetrate 18'' in gel. We're not there yet, but we're close enough. You gotta be careful though. Even the best performing HPs don't always open up in the real world. The HST pretty much passes the FBI protocols 100% of the time, but from what I've seen of actual autopsies, it's maybe 50/50 in real life. So regardless of what your bullet does in testing, always be aware of what's behind the target.
You can see from ballistics gel that FMJ and JHP do pretty much the same thing, except the FMJ penetrates further. That's why I say I would prefer FMJ if in an environment where bystanders weren't a consideration. In that kind of environment, there's no such thing as too much penetration. So, no, I do not believe soldiers were ever at any disadvantage due to not having hollow points. Food for thought: the Germans especially in WWII gave zero regard for the rules of war, and they had the absolute best small arms industry in the world. If they thought hollow points would have made their weapons deadlier, or even lengthened recovery times for wounded soldiers, they absolutely would have issued them without any further thought for what the referees would say about it.
Note that the dye in the first block exaggerates the wound cavity. Essentially, both blocks are showing very similar permanent wound channels. Also notice how both blocks are showing wound channels smaller than the diameter of the bullet; that's what I'm referring to when I say that bullet diameter is kind of irrelevant (as far as wounding is concerned, not in terms of sectional density and whatnot).