I think the issue here is that the game developers may not have any contract with PRS. Historically they wouldn’t have had to - they’d license the music from the big music labels, stamp their game onto a CD and sell a product. Now they’re not just selling a product - they’re licensing access to a “performance” of it. Valve is the playing an active part in this by “performing” the works on demand. It seems stupid to me, but that’s the world of content licensing.