We have noticed a few issues the way Microsoft is creating any version of the documents and consuming the allocated tenant storage.
Here is what I did:
I create a new document in a version enabled document library in an SPO Teamsite(with Group) and sync the same document library to my desktop using OneDrive desktop app. I co-author on the document with other users.
During Co-authoring, SharePoint creates multiple versions of the document. Every version of the document is consumed from the total storage quota allocated on the SPO site. If a 50 MB document has 500 versions(the default document library limit), it would consume 25 GB from the Site storage quota.
For every change in the document, OneDrive is downloading the full file to desktop instead of only the changes in the document.
Note: The upload of the change in document is working as expected. It is only uploading the change and not the full document.