Off the top of my head, maybe Morse talks about one of his recurring nightmares in his book 'Star Beast', wherein there's dozens of Aliens and Ripley has a gun and blasts them, and two competing indie game developers decide to make similar "retro" renditions of 'Star Beast: Morse's Nightmare'.
So the events of the SNES and Genesis games "occurred"... in Morse's head, in the form of a nightmare/PTSD recollection of 'Alien3'.