I think the documentation is outdated given that C11 atomics [1] and threads [2] are available for more than a year now. Same goes for pretty much everything MSVC frontend related stuff (I've yet to try which C++23 features are supported at the moment, but they've secretly added support for C23 features like typeof and attributes, as well as GNU Statement Expressions).
[1]: https://devblogs.microsoft.com/cppblog/c11-atomics-in-visual...
[2]: https://devblogs.microsoft.com/cppblog/c11-threads-in-visual...