Re: 'It's not clear whether he also has a FB account or whether he's a non-account'
I think it's more the manner in which it's queried.
In the sense that for an advertiser, you know that user I'd "xyz" likes this and that and so can target adverts.
But that doesn't necessarily mean that for a Facebook user or non Facebook user that you could very easily associate a user id with a an actual identity provided as part of the SAR. Especially if what they say about the two platforms being unrelated (if I remember the article correctly)