I'd think most PC games and other desktop GUI software runs on windows and looks like it runs on windows.
Right.
Most PC games currently run on Unity, which doesn't care whether it's running on Linux or Windows. I'm not aware of whether PlayStation runs a Linux kernel, but I would bet it does, since they wouldn't get a good price from MS on OS bulk licenses. When the game is installed on a Windows PC, it's obviously running on Windows. When a game is on any of the various (non-Microsoft) game consoles, odds are it's actually running under a Linux Kernel.
And I'd imagine that a web browser on windows isn't secretly a Linux environment.
True. I would argue that's running half on Windows, of course. The other half, the server, had about a 99.7% chance of being Linux, today. Mostly Amazon Linux running in AWS. Even websites recently developed entirely on Microsoft libraries, and served in Microsoft's cloud service Azure, are largely running under a Linux kernel.