Wow, that is... lame.
In fairness, what could they really have done? There was no way for FG to be a known Trek character and have a shocking "It's me, Austin! It was me all along Austin! Bwa-ha-ha-haaa!" reveal. Only to logically extrapolate a backstory from what we knew.
This sort of reminds me of a recent plot on Doctor Who. Series begins with the Doctor's apparent death and half way through the series, after one potential answer that turned out to be a red herring, the actual device is introduced that's obviously going to be used to fake what we've been shown. In a sense it's a total cop out, being a solution which clearly could never have been deduced from the evidence presented in the opening episodes.
Simply the same kind of narrative trickery to explain something the series creators had absolutely no idea how to resolve when they first set fingers to keyboard.
In a war with factions across time, the future is presumably where the high ground is occupied. That's where one side have presumably invented all the tech which allows the existing timeline to be monitored and also stand in a chamber, isolated from the changes. A character would be introduced as a threat native to the 22nd, be played around with for several episodes - only to be revealed as allied with a future race and relocated to the 29th... where his actions retroactively prove to have been the Suliban's shadowy benefactor. Before returning again, to instigate the Romulan War (after Season 4's arc left the technology behind the Drone project in doubt) and then be killed off in the final season or series finale.
Alternatively, FG as a far future decendant who wouldn't even exist had it not been for the actions of somebody in 22nd. Or his own, in a closed off paradox.