Moving folders · Folders an app is using
Why isn't Spotlight listed as an app using my folder?
Short answer: macOS's own background services, like Spotlight indexing, are deliberately left off the apps-in-use list. They can't be quit and don't interfere with a move, so only apps you can actually close are shown.
Because macOS's own housekeeping services — Spotlight indexing and the like — are left off the apps-in-use list on purpose. They can't be quit, and they don't interfere with a move in a damaging way, so listing them would only give you something you can't act on.
Only apps you can actually close are shown, each with a Quit button. See What does the progress sheet show?