I think this is just coming down to semantics. That huge ~50Gb download is just studio stuff, forget about that if you don't need it. But part of the sideloader modpack is already included with the main game. If you run the updater (via initsetting or kkmanager), you're using it. The updater gets new mods and puts them in various folders under \mods, like \mods\Sideloader Modpack\Hanmen for the recent freely released Hanmen skin shader. All kinds of clothing, hair, accessory, tattoo, map, shader, etc. mods get updated that are used in the main game.
And everyone should take note of this - all the mods in the various Sideloader Modpack subfolders are maintained by the updater - the updater will add *or delete* files from these folders. Files saved in mods\MyMods are not controlled by the updater, and should be safe from deletion. So any paid mods you may have, mods you've personally downloaded and installed, or ones marked for deletion you want to save should go into \mods\MyMods. The updater will show new files in green, files to be deleted in red, so look at the file list before pulling the trigger.