Exactly... 10mm isn't moving fast enough for to cause damage like a high power rifle round would. All 10mm does is poke holes just like other calibers. The extra energy simply allows some 10mm rounds to have enough energy to poke deeper holes. That may may a different with a big 4 legged creature with thick fur, muscle, fat, and bone thus allowing the bullet to better reach vitals, for self-defense against humans, it's pointless IMHO. I've seen simular grain JHP bullets in 40s&w and 40s&w darn near expand to simular diameters, but the only difference is that 40s&w may have gone 18"-19.5" and the 10mm an inch or and inch and a half further. Both rounds not hitting vitals aren't going to stop an attacker unless they choose to. Both rounds hitting vitals will shot a threat. Those who think 10mm is going to necessarily give them the "one shot stop" or kill someone deader just because it has more energy/velocity to travel a little further (often over penetrating), and just fooling themselves.
Also, the 10mm JHP that's typically sold is designed to somewhat fit into the FBI standards most expect from their JHP self defense rounds. It's usually under powered, yet those who typically carry the ammo will pontificate about how much more powerful their 10mm is while craving on 40s&w when they both perform similarly with similar expansion within FBI specs. Yes, you might get more velocity out of the 10mm, but both 10mm and 40s&w will be engineered to be within FBI specs regardless. I don't care how much velocity you get, but rather how is the round performance down range vs other rounds and how does that translate to giving you an edge in a self-defense scenario.
You can't tell these people anything because they usually become defensive and start talking about velocity, velocity, velocity and will ignore everything else. They think that because their slow handgun round (in relation to rifle rounds) has more velocity that they're doing so much more damage. They're still just poking holes. There's just diminishing returns with using 10mm for self-defense against humans and even many animals.