But then they would show the general public that Linux is a thing worth mentioning. I doubt that many people outside IT know about CBL Mariner.
i think they are already mentioning it: MS has a help webpage on how to install linux, both WSL2 on Windows machine, or how to burn iso and install linux on bare metal. https://learn.microsoft.com/en-us/linux/install
Microsoft have quite a bit of software that runs on Linux (PowerShell, VS Code, .NET, Azure tools, Intune / Endpoint Manager, even SQL Server) so it’s understandable that they’d have documentation to explain it to their customers.