Mac quarantine seems a bit eager. Shows these scary alerts when opening files with the quarantine flag that are set to open with anything except the default app (the com.apple.quarantine and com.apple.LaunchServices.OpenWith extended attributes). This is macOS 13.4.1.

Mac alert: "1979-12-MVC.pdf" cannot be opened because it is from an unidentified developer. &10;macOS cannot verify that this app is free from malware. &10;Preview created this file today at 11:05. &10;OKMac alert: macOS cannot verify the developer of "1979-12-MVC copy.pdf". Are you sure you want to open it? &10;By opening this app, you will be overriding system security which can expose your computer and personal information to malware that may harm your Mac or compromise your privacy. &10;This file was downloaded on an unknown date. &10;Open &10;Cancel

Douglas Hill @douglas