In KN's metrics inspector, the file, which was originally, say, an .mp4, is sometimes, but not always, seen as having been converted to .mov. I've seen this myself, it doesn't always appear, but sometimes, and I don't know why it's sometimes true and sometimes not. So this is my theory (disclaimer: I'm neither technically informed nor expert, but simply a frequent user, who likes to try all kinds of things out): KN, when it imports an audio, and probably a video file, too, makes it a .mov file, so it can be used more easily by QT, which seems to be KN's media presentation format. KN makes this conversion all by itself, it's coded into KN. Then, once the KN presentation has been saved, the whole shebang is saved together, and KN kind of swallows the QT whole. The QT .mov file is no longer a separate entity, but part of a whole KN doc. Perhaps someone expert in programming and doc codes could separate out the QT file afterwards, but the average user, however anal, will be unable to do it.
And it might well be a senseless and thankless task, even for the expert. The original audio or video file can be easily (depending on your expertise and the programs at your disposal) edited on its own, quite apart from any connection to KN. So the easiest method for anyone, even the expert, would be to do the editing on the original file, delete the unwanted unedited file from KN, and insert the edited one.
The question, at bottom, seems to be this: is someone most interested in doing something efficiently, or more interested in how something works, regardless the benefit (or not) of simply knowing, which may be its own reward. Those are two different goals. The answer to the second may sometimes point to why you don't do something, and not always just to how you can.