I don't think any of these companies use Rust much. You may find teams here and there using it but the vast majority of the Rust type stuff is written in C++ or Java.
UWP/WinUI foundations are in C++ and .NET.
Azure Sphere, despite all the security selling marketing uses C based SDK.
Windows kernel seemed to be in the right direction adopting more C++ and less C, specially with the userspace drivers COM SDK, but they just reverted to more C support on the latest versions.
So in what concerns Microsoft, I look forward to their Rust's adoption, although currently its adoption is yet to be reflected on the Windows development ecosystem.