> Generally not. Otherwise, a "run" would degenerate into starting the game, saving at the first opportunity, then loading a save which has almost completed the game and finishing it from there. That's clearly not a meaningful or interesting competition.

This doesn't make any sense. If you can do that with two savefiles, you can also do it with one savefile. Start the game, save, end your segment, play through the rest of the game without recording it, save, start your second segment, and defeat the final boss. Voilà.

That doesn't work because the segment following another segment must pick up where the earlier one left off, which is just as possible with multiple savefiles as it is with one.

It's legitimate, for example, to play through segments 1/2/3/4/5, then go back and redo segment 2, and then continue on from redone-segment-2 to an all new redone-segment-3, which has lost all pretense of existing in the same timeline as the original run did.