At the end of the day, AVP is a FPS.
Anyone who is laughing at this thread, just google the game and you'll see everyone calling it that. No 1990s reviewers called the game "a simulation" just because the guy in charge of writing the instruction manual called the game a simulation. It's a corridor shooter which they compared to Wolf3D and Doom at the time as those games were the posterboys for FPS.
Just because a shooter has some branching elements to the map (which just about every RPG dungeon or shooter level has) does not mean it's an "open world system". If that's the case, then old ass Wizardry games tracked on graph paper were open world because you could walk around to different parts of the levels until you got stuck needing a key or solve the riddle BS.