Just clarifying, I didn't mean "they" as in "this studio", rather "those owning the XCOM license*". Basically, there's already an apparently ongoing series of new XCOM games which stay pretty close to the original formula and appeal to the core fanbase of the franchise. If they (*) are producing another XCOM game at the same time, it would be kind of silly for them to make the same game twice.
I wouldn't mind different, but within the bounds of the series' story. There already being a "proper" successor does not justify one that's completely detached from the series' setting. Like I'd be somewhat happier if Van Buren was released alongside Fallout 3, but I'd still consider FO3 a boring piece of level-scaled, poorly written garbage.
And seriously, what's this game got to do with XCOM? If you renamed this game, there would likely be no trace left of anything related to any other X-Com/XCOM game. Not even in the new XCOM: EU does anyone ever refer to this, nor is there any equipment from that time. That's not how good prequels work, this is a shoddy retcon.
Who ever asked for this "origin" story? The origin story of the organization is "Aliens here and now. Alliance of nations creates organization to battle aliens.". Nobody asked for a "true" origin, cause the origin was already there. Like from the 60s you may as well go further back and justify the lack of any trace by making Amish people the protagonists of the game or whatever, and say "That's the true origin of XCOM! Isn't that what you always wanted to know?". There's no purpose to this crap, other than possibly for 2K Marin to cash in on art assets left over from Bioshock 2 (or maybe even a cancelled Bioshock 3).