Alien Isolation 2 uses legacy Xenomorph animations from the first game
Creative Assembly principal environment artist Archie Whitehead explained at Gamescom that Alien Isolation 2 utilizes motion capture data originally created for the original title.

Studio lacked technology previously
The development team did not possess the necessary technology to implement these animations when they worked on the first game. Whitehead noted that releasing the sequel twelve years later provided a benefit by allowing the use of this older data.
New animations improve responsiveness
The current version of the Xenomorph is described as more responsive and reactive than its predecessor. These improved transitions make the creature appear scarier to players during gameplay.
Player perception drives fear
Whitehead stated that intelligence regarding the alien relies heavily on how players perceive it visually. Using a flamethrower or hiding in lockers will be less effective against the Xenomorph because of these changes.
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