NextCloud keeping local copy of files when using Sharepoint backend


I have a question in regards to the sharepoint backend - GitHub - nextcloud/sharepoint: 💾 Nextcloud SharePoint Backend for External storages . I configured it using the Github instructions.

  1. Then for test, I tried to upload a file to the main “Documents” folder, linked to the sharepoint, so far so good - the file appeared in sharepoint.

  2. Then I deleted it in sharepoint and it was moved to sharepoint trash. I then emptied the sharepoint trash.

  3. I deleted it in sharepoint trash and found the file still present in nextcloud trash, so I deleted it from nextcloud trash as well.

The question is: When using sharepoint backend (I clicked on the sharepoint icon), why does Nextcloud still leave the uploaded files on the local server? This would require me to have same capacity as sharepoint in the local server, which kind of defeats the purpose of using external backend. How is it supposed to work?

Anyone knows anything? Please?