I am sure that they are well aware of this. The issue is that the total compute time to compile their build is significant, and significantly (several multiples of 2) reduced by going to c#. Compile time increases development costs, execute time increases hardware costs.
Which, in case you didn't know, the MSFT build stack was able to do with C++ projects long before it could with C# projects. I wonder if wglb's referenced company would have liked to know that. ;)
True, last I checked MSBuild support for VC++ projects was lacking. I think their solution was to run the build through the visual studio command interface...hopefully it's gotten better.