I think it's a bit of both. Obviously at the end of the day, it's a fanfic. Though I would like to GameTheory that this coulda happened.
(My story Spoilers??:)
I very much support the "Ghost isn't dead" propaganda so I wanted them to live. I then thought about COD overall and was through some loose connections saw that the Ghosts and even Advanced Warfare story lines are connected. Just a bit, which is why Elias Walker and the gang show up :)