I think it's the same in Windows, right? Can't use the syscalls underneath the hood, everything through the standard libraries. Maybe I'm wrong (I know very little about Windows other than how to use it to play games, and WSL)
In this particular case, the Windows APIs have neither getaddrinfo() nor getenv(); and the closest equivalent GetEnvironmentVariableW is perfectly thread-safe. Microsoft additionally has a C runtime (msvcrt) providing functions like getenv(), but this is much less fundamental than it is on other system. Every program is supposed to ship its own copy of the C runtime, it's not officially part of Windows! And it's perfectly possible for multiple different copies of the C runtime to be loaded into the same Windows process. And since *environ is a variable defined by the C runtime, there's a different copy for each C runtime...
https://learn.microsoft.com/en-us/cpp/windows/universal-crt-...
Doing raw syscalls without ntdll is also possible, but windows syscall numbers change on essentially every release, so you’d end up with something that only works on your windows version.