Upvote:2
Is this not required as part of the application?
Since it is not mentioned in the required documents list that means you are not supposed to supply it with the application.
If not, how is the link made between my application/GWF number and my documents?
I don't think you should be bothered about that. There are various ways they can pull out your application from their system (one of them is your passport number being associated with the GWF). Also, when you submit an application through TLS, they put all the documents in one envelope under a GWF. VFS might be doing the same.