Even if you use Windows' LZX compression, it only reduces the size from 11.9 to 11.8GB. Meaning the files have some form of compression already, they're not just left there in full fat bloat mode... so it probably has a bunch of crap in there which isn't even used.
Though, I'm far more concerned about this game bringing anything that's not an RTX 4090/5090 to its knees, & the dev not using the UE4/5 plugins that are available to add smart upscalers like DLSS/FSR4 to band-aid the lack of optimization. My Radeon 9070XT weeps.