The first reason seems possible I guess, but not likely as being the only reasons. The second reason though should only imply that you lose the compression, not

The first reason seems possible I guess, but not likely as being the only reasons. The second reason though should only imply that you lose the compression, not that you're unable to produce the file in the given format in the first place? What I'm referring is that I recall encoder tools outright rejecting high resolutions for older formats.