Freeing up space · Stopping, undoing and apps in the way
Why doesn't the apps-in-use list show Spotlight and other background services?
Short answer: macOS housekeeping services like Spotlight indexing can't be quit and don't interfere with a move, so they're left off the list. Only apps you can quit and that matter are shown.
Because they can't be quit and don't interfere with the move. macOS's own housekeeping services, such as Spotlight indexing, often touch files briefly; listing them would only show you buttons that can't work.
The list in the confirmation sheet shows the apps that matter: ones you can quit and that would genuinely get in the way. See Move when closed.