Ah, I thought that's what you meant
Yeh, I very much doubt 2015 would be so bad at game designing to have forced their game to load all current pk3 information into resident RAM memory before you've even started a game up.
If they did then you'd effectively have around 1 Gig of info trying to be forced into your RAM, which would surely not work on most machines
I'd imagine it works like just about every other PC game out there and only loads what is needed into RAM then discards it when it's no longer needed (only saving info in a cache that can be re-used if the PC has enough RAM to support this).