Some, not all, iCloud files have the com.apple.quarantine attribute. Why?

Investigating why some files that I've been working on show up in Finder's Recents folder, and others don't, I notice that com.apple.lastuseddate is not being updated after I save the file.

However, after I delete com.apple.quarantine attribute (with xattr) , the "last opened" date (com.apple.lastuseddate) is updated after working on the file and it appears in the Recents folder.

The files were never downloaded. They were created in the (iCloud) Documents folder on the same Mac with applications purchased and installed via their manufacturers' installation apps rather than purchased on the Mac App Store. Would this make a difference? Presumably I needed to give permission at the time for the installers to install to the Mac and so there should be no issue with files that these apps create subsequently.

Strangely enough, files from one particular app consistently have com.apple.quarantine set, from another they do not. Is MacOS looking for something in the apps and can I turn it off?

I do not wish to turn off quarantine for all apps installed in the future with

sudo defaults write com.apple.LaunchServices LSQuarantine -bool NO  

... but maybe this is the only way?