Like, watch this video: https://www.youtube.com/watch?v=9XWxsJKpYYI
This is a whole story about how the liquids in the bottles ‘isn’t really there’ and how it’s not a ‘real physics simulation’ - all just completely ignoring that none of this is real.
There is a sense in which the bottles in half-life Alyx are ‘fake’ - that they sort of have a magic painting on the outside of them that makes them look like they’re full of liquid and that they’re transparent. But there’s also a sense in which the bottles are real and the world outside them is fake. And another sense in which it’s all just tricks to decide what pixels should be what color 90 times a second.