Yes this will, in both classic and modern be saved as a new version (I believe). Some time ago Microsoft changed the default version setting in SPO / OD4B to retain 500 copies. If you use the web app to allow multiple editing, these auto saves will also be visible in the version history.
It does not generate a version everytime the document is autosaved, but let's say if you are doing a lot of modifications, you are going to have a lot of versions generated what's not a problem since SharePoint can handle them
