There's also the people like me that couldn't historically run certain games well directly on Linux, so we have Windows virtual machines with GPU passthrough. Which would read as me being a Windows user in the Steam stats, but a Linux user in other stats.

The state of gaming has improved drastically since I started doing it that way, though, and I'm considering ditching the VM entirely. Multiplayer games seem to be getting the hint about anticheat exclusion on Linux. ARC Raiders, for example, is a competitive game and runs flawlessly directly on Linux.