Does Windows set up dual-boot if Linux is installed first? Naw.
Does Windows read or write Linux filesystems? Naw.
Has MS open-sourced any significant or important parts of Windows where it won't benefit directly? Naw.
It is in MS' direct interests if PowerShell or .NET are supported on other platforms; it makes them more credible tools.
Did we get source for Explorer or anything? Naw. Calculator. Big fat hairy deal.
Has MS open-sourced any obsolete products that might actually be of use or interest, such as the final versions of MS-DOS (25 years old) or Windows 9x? Naw. They contain things like Explorer and so on that are still used. Can't go actually _helping_ people.
It's all marketing flim-flam. Don't believe the hype.
Linux is doing great on phones and servers and so on. On the desktop, only ChromeOS is not a rounding error. So, if MS can embrace-and-extend the Linux desktop, and make Win10 a better desktop Linux than Linux, then it helps MS and it helps Win10.
And with what it learns from that, it can apply to WSL in the datacentre and on Azure, where it can make Windows Server a better Kubernetes than Kubernetes.
Which, let's face it, would not be all that hard.