Not sure what you are referring to as implemented natively in GNOME.
One crucial difference is the fact that Backup and Sync picks up local files (which exist physically on the user's machine) and uploads them to a special Drive directory in the background. GCSF does not store anything locally unless you tell it to. It simply creates a virtual directory and reports its content and file tree structure so that it matches whatever exists on Drive.
I think GP is referring to the Gnome Virtual File System (GVfs) [1], which has a number of pluggable backends, one of which being Google Drive. I've used it lightly and it seemed to "just work."
