I'd agree with you, except for one thing--and I'm sure you're aware of this too: some people, fueled by certain drugs, obtain super-human power, and a gunshot to the floor--or probably even to their foot--wouldn't stop them. I absolutely agree that shooting a living being (human or otherwise) would be very, very difficult for me, but in that situation, I think my own adrenaline would kick in enough to make it possible. I wouldn't want to kill them and have to live with that on my conscience, but I would want to stop them AND make a really good, long-lasting point, like "you did something bad, now pay for it!"Something to keep in mind... If a threat is detected there really is no good reason to wait until there is an actual confrontation. Most thieves are after goods they can easily liquidate. Not knowing what might be had for the taking at a given residence, they aren't likely to risk a gun wound for whatever. Shoot a hole in your floor. The gun report will most often be unexpected, respected, and send the bad guy scurrying.
It's easier for most to pull the trigger when it's not pointed at someone. And with a revolver, you most likely have five more rounds for that groin shot if necessary.

Also, if the dude ran off without being shot, there's much less chance of catching him--and he belongs in jail, not free where he can pull this on someone else.
Hopefully, this will never, ever happen.
When I had my beautiful, protective Great Danes, plus a monitored alarm system, I felt very safe. Now we have our 15-year-old mutt who weighs about 50-ish pounds and wouldn't hurt a fly. (Of course, my Great Danes wouldn't either, but at almost 200 pounds, they LOOKED so intimidating, no one wanted to take a chance.) Between her and the alarm, I'm not sure how scared a seasoned and/or determined burglar would be!