System Data iPhone 13 Pro Max Storagegate

Anything synced to iCloud will retain its data. But, system storage is managed by the device. There isn't really a need to wipe your device. It's typically full of cache files and streaming media, and other system related files. Space can often be freed by restarting your device, performing a backup, or removing media files).

You may have corrupted storage, which can be caused by an interrupted sync, or sometimes just randomly.

Back up your phone, reset it, then restore the backup you just made:

1. How to back up your iPhone, iPad, and iPod touch - Apple Support
2. Restore your iPhone, iPad, or iPod to factory settings - Apple Support 
3. Restore your iPhone, iPad, or iPod touch from a backup - Apple Support

Your title alludes to the activity of “plumbers” in a long-ago era, and understanding “Other” storage usage in this era is all about understanding the app and network plumbing.

“Other” is user and Apple apps that cache locally-generated data and cache iCloud data locally, including Photos, game data, mail, files, and whatever other data that the apps in use want to need to have available locally whether for technical or performance reasons.

”Other” is storage you’re not presently using, and that the apps and iOS and iPadOS are then managing as a cache. Unused storage that can be used as a performance cache is wasted storage. Frequently-accessed remote data is better off being locally-stored data; cached.

Restart, or backup and reset and restore certainly, but for most of these cases, the “Other” storage usage comes right back, because that’s how iOS or iPadOS and the apps can best support your activities.

Where did ‘Apple admits’ come from? Apple’s documentation recommends this as an important step when Other is abnormally large. And it DOES work if the storage problem is caused by storage corruption, because the backup is app-by-app, database by database, and thus does not include corrupt storage, so any storage corruption is not in the backup, and thus will not be restored. If backup/restore does not fix the problem you simply have too much stuff on your phone.