Content Sync provides you a couple of different update behaviours you can configure. See Pull updates here for details: Flow Pull Options.
One of the available options is to allow editors to override content locally after it has been pulled:
As you can see, the content form will only be visible after the editor explicitly flagged the content as overridden and the consequences are explained to them:
Remote changes of this content on the source site will be ignored.
However, if the content is deleted on the source site (and deletions are configured to be propagated), the content will also be deleted on this site.
If you uncheck the box later and hit Save, the content will be immediately reset to match the content from the source site again.
The content will be flagged as overridden in the content list (see here: Sync State).