Why was this suddenly required?

Check your preprocessor macros. For me _WINDOWS is present

If anything _WIN32 should be the only one used as its set by the compiler unconditionally? Having them all is suboptimal.

Yes maybe make a pass and just use _WIN32 everywhere? Do you still have this compile error?

https://learn.microsoft.com/en-us/cpp/preprocessor/predefined-macros?view=msvc-170#microsoft-specific-predefined-macros

_WIN32 Defined as 1 when the compilation target is 32-bit ARM, 64-bit ARM, x86, x64, or ARM64EC. Otherwise, undefined.

looking at documentation i agree we should just use _WIN32 instead of _WINDOWS just make simple and standard

Updated it to use _WIN32 instead of _WINDOWS

There are 48 files using _WINDOWS in this project, but only 11 files edited here.

Found and updated all 48 files