The dynamic grass system is also another good source of inspiration and technical direction. https://www.unrealengine.com/marketplace/dynamic-grass-system
Was Demo 2 an in game Particle/Physics system? Not certain if was in game or not? If these are in game physics and particle systems they seem more advanced then HL2.
No it's not. Get that garbage out of your head. Shake it off and stop thinking that. You are asking why don't people take bicycles to the moon. It's not a bad question if you honestly didn't know any better but don't ask the question to confirm what you already think is the answer and then bull headily pursue it as if you…
@Fabi_G ah you're right! Setting it to Grass mode instead seems to fix the bake issue, though now I'm dealing with another issue with the built in wind system.