It is very true indeed.
Okay, but--once again, the objective is to defend against an imminent threat--not to "end the threat".
It the threat is still imminent, that's one thing. There may be circumstances in which a man who has threatened with a firearm and who appears to no longer be attacking may well still pose an imminent threat. For example, a suspect who is retreating with his firearm could easily turn very rapidly and shoot again. Shooting would likely be justified. Were he armed with a contact weapon, that would be a different story.
But if a man waves a gun at me or shoots at me and then heads away and may be around a building, I have no business going to "get him". The window of imminence has closed, even though he is still armed. The immediate danger to me has passed. What he might to later is speculative.
That is the problem with comparing competition with defensive shooting. The competitor will try to score hits on the target, but the "reasonable person" will avoid further danger.
I'll agree with most of this. When we use the term "end the threat" its important to note that this is exactly what is meant. We are not ending the "bad guy" but rather the threat which is a combination of bad guy, weapon, intent, and imminent ability to carry out the threat. If any one of those goes away the threat is ended.