They are using modules in the MS Office team:

https://devblogs.microsoft.com/cppblog/integrating-c-header-...

This is untrue. The MS Office team is using a non-standard MSVC compiler flag that turns standard #include into header units, which treats those header files in a way similar to precompiled header files. This requires no changes to source code, except for some corner cases they mention in that very blog post to work around some compiler quirks.

That is not the same as using modules, which they have not done.