Why can't setblock, fill and clone just load their own chunks to work? They are already modifying the the blocks placed there. I don't think it would be hard for the game to quickly analyze the Coordinates entered into the command, and load the corresponding region file and chunks that the coordinate area is within. /tp does this.
This would make so much more sense rather than using /spreadplayers, which was never meant to be used as a chunk loader. Using /spreadplayers works for many cases, except I have been running into some issues in 1.13 with my integrated server getting hung up trying to place a couple structures far away from loaded chunks and from spawn chunks as needed in a dynamic adventure map. I just simply cannot see why this functionality does not exist.