I'll throw in my two cents.
I agree that this is all about semantics regarding what we think a word means which was invented by our own community. To me, it all comes down to what do we think people meant by this term back in the early 2000's or before -- when the term was first "widely" used, and when it became a more mainstream term by its usage in the KOK movie. In other words, what did THEY mean when they used the word (or phrase) "killscreen" (or "kill screen") in the movie?
"Hey, there's a potential Donkey Kong kill screen coming up if anyone's interested..."
In my opinion, if you really think about what those guys were saying in the movie when they said "kill screen", it simply means "the screen on which you are killed". So, the kill screen is screen 22-1.
With that being said, Ken's points are well taken. I will agree that in order to "get to the end of the game", or to "beat the game", you need to play until you are killed by the Timer bug. (In my opinion, having any one of your men killed in this manner qualifies as beating the game.) Having a list such as "Official, unofficial list of kill screen players" creates sort of a gray area and should simply be qualified specifically by the list creator -- are we recognizing all players who have reached 22-1 or are we recognizing all players who have reached the end of the game? Again, in my opinion, these two things are not the same. I suppose if there exists any players who have reached 22-1 and who have NEVER reached the end of the game on ANY of their games ever, perhaps they could be included on such a list with an asterik which explains that this person did not reach the end of the game. I dunno.
So, yes, these are two different things. But I believe that the term kill screen refers to screen 22-1.