macOS has an elaborate set of rules determining which types of xattr are preserve during different types of copying, including syncing to iCloud Drive. Here they are in full detail.
iCloud Drive
A brief reference to excluding items from being backed up, from Spotlight indexing their contents, and for them to be copied up to iCloud Drive.
Unless you exclude them from backups, Time Machine will back up all items in iCloud Drive as long as they’re stored locally when the backup is made.
Consider the fidelity of backup copies, the speed of a backup method, and the risk of losing the contents of that backup. And test backups by restoring samples from them.
Introduced in OS X 10.7 Lion in 2011, this feature has undergone considerable change. Although it stored versions in iCloud Drive at one time, it doesn’t now.
How one of the serious bugs in macOS Sonoma 14.4 came about, why it was so serious, and how Apple released a fix in 7 days of it being reported.
Convert a document into a folder containing all its saved versions, and unarchive that folder back into a document with all those saved versions. All using drag-and-drop.
How to reproduce this serious bug in Sonoma 14.4, and how to archive all the versions of a file or document so they can’t get destroyed.
Do you use saved versions in documents? If a file is evicted by you or macOS, then all saved versions will now be removed, and lost forever. How to work around this serious bug.
Step by step through moving to iCloud Drive, eviction to a dataless file, materialisation of local data, editing and syncing with iCloud Drive.
The Eclectic Light Company 