I understood your question. What I am pointing out is that when you submit an artifact to FB, it is a trivial matter for them to store as 'extended-attributes'

I understood your question. What I am pointing out is that when you submit an artifact to FB, it is a trivial matter for them to store as 'extended-attributes' your facial biometrics. This has nothing to do with the ML pipeline that munches on data in the aggregate. As to whether it is possible to extract such information, per my understanding the internals of ML pipelines are rather opaque, so it would be non-trivial, if not impossible. I have no idea either way.