literally everyone ever who bitched about the shortness of GZ didn't know about this. they released the prologue as a teaser because the final game at the time was a year or three out from announce time. this shows off their new in-house, photorealistic engine, and gives a teaser of what the new gameplay will be like. it also jumps the story from the 1970s to the 1980s, showing how the coma happens. and the preorder special editions get exclusive mother base personnel upgrades from their save files, when TPP hits.