Horizon Forbidden West uses some form of character Lighting, a direct lighting source that will always shine on Aloy, but not her surroundings. It will cast highlights and shadows even when there's no direct lighting, no direct shadows visible in the scene. The character lighting will switch according to surroundings, sometimes visibly a bit late – like at the beginning of the video, when Aloy steps into the cave. For a while, there's still the lighting visible that fits the outside, but not the inside of said cave.
Horizon Forbidden West Statistics For PCGH (english)
PCGH (english) presently has 2,136 views for Horizon Forbidden West across 3 videos, and less than an hour worth of Horizon Forbidden West videos were uploaded to his channel. This is less than 0.48% of the total video content that PCGH (english) has uploaded to YouTube.