How does Google lock you in when you could just export it as docx and move over anytime to Word/Libre?

You can even bulk download as many docs you like and there's even takeout.google.

You can also export files from Microsoft products. There is no difference in vendor lock in between Google and Microsoft.

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.