I thought all it did was to create symlinks with the proper prefixes in a automated way for a given script, something that one could do manually... but apparently it does something more.
But perhaps I just did something wrong when trying to do it manually, like using the wrong runlevel folders. Or perhaps it was just the difference from priority 20 to 19 that made the difference even though I thought the key was to be a higher priority (i.e., a lower number than) than 22.
...