Crickets...

Indeed, I came to a dead end as far as imitating the front end. I got farther than I thought I would, though. I like that MathLink is transparent enough to at least give a glimpse of what is going on.

Another approach I thought to try was to override a function within Mathematica. For example, I tried this, using an access token than I had retrieved with my own code:
But then when I try this:The regular oauth dialog pops up, as if the function had not been overridden. Have I done this incorrectly? Or is this function somehow locked? I tried using "unprotect" but that had no effect.
Also, this dialog looks different than the one that pops up when I use SocialMediaData, so I am not sure if SocialMediaData even uses this function. So, perhaps there is too much reverse engineering required altogether in this endeavor. But I thought I would give it a shot.

If there's no supported way to do this (as it seems), reverse engineering it is going to be rather difficult because all the relevant symbols are Locked.

I think that if you want to provide a service like this, you will need to create your own Facebook application that will help with exporting the data (and you'll need to take responsibility for it as a Facebook app developer).  It'll need to be authorized in a similar way to how SocialMediaData is.  Before this function was available, I used NameGen, which may be helpful for you to study how this works.

The documented version of Developer`UseFrontEnd is UsingFrontEnd.

I'm accessing JLink from within a web server, so it can't open a front end that the client can see. P.S. the original post says "updating name" but it was me. Not sure why except maybe I posted too soon after creating the account.