The question is how do you export and use metadata from sharepoint that is useful? Documents are not where the lock in is.

Microsoft Office, Teams, and SharePoint have comprehensive APIs so you can export any metadata you want. It's no different from competing Google products in that regard.

Developer work is expensive and beyond most users abilities. File..save is not. It is very different.

You can do File, Save As in the Microsoft products as well. There's no significant difference.