… it's also true that file sync use case FinderSync Extensions were designed address has been largely replaced by the newer (and superior) replicated file provider architecture.
I'd like to comment on this. It's true that current documentation says:
Use this framework when you need to synchronize the contents of a local folder with a remote data source. Then provide visual feedback to the Finder…
However, the initial documentation was't that strict:
Finder Sync supports apps that synchronize the contents of a local folder with a remote data source. It improves user experience by providing immediate visual feedback directly in the Finder
The word "supports" doesn't imply a limitation (English is not my first language, so I may be wrong). I believe many other developers understood it the same as me, especially considering the fact that Finder Sync extensions provide a way to add custom menu items to Finder's contextual menu. I think most developers saw it as a sort of continuation of old CMPlugin API from MacOS (yes, the capital 'M') 8/9 days, which was available until Mac OS 10.6 Snow Leopard. It's seen as a way to extend Finder's capabilities, by executing custom operations (not limited to "synchronize the contents of a local folder with a remote data source") on files selected in Finder.
I think I know about 50 - 60 applications embedding Finder Sync extensions at the moment, and only a dozen of them actually "synchronize the contents of a local folder with a remote data source", mostly coming from huge and well known cloud providers (Dropbox, Google, Microsoft…). All others, mostly coming from independent Mac developers, offer some custom operations of files selected in Finder, nothing related to any sort of syncing. I believe MR_Noodle's case is the similar one, "outside of its recommended use case".
Taking the above into consideration, I think it'd be a huge mistake for Apple to discontinue and deprecate Finder Sync extensions without providing functionally equivalent replacement. That would break a lot of third party Mac software and render those applications completely useless. I say that because I'm starting to think that's actually going to happen. First we had "Finder Extensions" settings section missing in System Settings on Ventura (it was there in the early versions, but disappeared in the latter ones), leaving "Added Extensions" as the only place to manage Finder Sync extensions on Ventura and later. And now "Added Extensions" is missing as well. Similar actions on Apple's part in the past usually meant deprecation of technology and I'm afraid this is such case, but I really hope it is not!
I'd appreciate if this comment is somehow passed to people in charge of future development directions of macOS and that they will seriously consider what was said here. Thanks a lot!