For trademark safety, this is the correct approach. You can say "Blah for XXX" and that's fine but if you say "XXX blah" then you can get into trouble.

Is this really true, or is it just something people have repeated enough times like 'nuclear Ghandi'?

I mainly ask because Microsoft has another product called Linux Integration Services: https://www.microsoft.com/en-us/download/details.aspx?id=551...

It's not a rule, it's just convention. Trademark law is about whether there is confusion about who made the product but not specific wording. Using "Blah For XXX" wording just makes it clearer.

"Tool for Windows" vs "Windows Tool"

The latter sounds much more like it could come from Microsoft. People repeat this because it avoids this confusion but it is not mandatory. A few projects on Github have had to be renamed because they've been challenged and the accepted solution from the trademark holder has has been to switch it around and become "for XXX".

In the present context, I'm reminded of IBM's "OS/2 for Windows", which, while actually a reduced-price version of OS/2 2.1 that used a customer's existing copy of Windows 3.1 to avoid the cost of licensing the Windows 3.1 components IBM shipped with OS/2 to support Windows compatibility, was also a marketing ploy to reposition OS/2 as a Windows enhancement rather than a replacement OS (which, to be fair, is not as misleading as it may sound, since OS/2 2.1, unlike Windows 3.1, is capable of memory protection and preemptive multitasking between Windows applications).

That makes sense, although in that case personally I would have named it Windows Linux Subsystem.

What if you just apply for a free sublicense and you get approved and your massive cadre of attorneys aren't fighting each other over 5 letters?

Apparently some HN people think that MS is so sleazy that they will just go "GPL yoink" and start running/advertising/supporting Linux without notice or consent the benevolent dictator. That's projection.

As a lawyer trained in trademark law, I've never heard this. Do you have any references?