“Editors like Textifier, Xcode, or Obsidian, lacking conflict handling, leave iCloud to decide which version to store on your disk and in your backup.”
iCloud Drive invented a sync conflict on files that were never opened on the iPhone, then quietly picked a version and threw away new paragraphs and code. Dropbox keeps both copies side by side. Apple hides the conflict unless your editor happens to ask. Time Machine and Backblaze then back up the wrong file until the right one ages out. Apple pushes you to put Documents in iCloud and then makes the data loss invisible.