SDL_assert: _exit() vs _Exit()

Is there a specific reason why SDL_assert uses the POSIX-function _exit() (along with a unistd.h dependency) instead of its C99 counterpart, _Exit()?
I’ve been stumbling across this, and would like to not have to add POSIX-wrappers as a workaround just to make SDL work.

Maybe in practice _exit() is better supported (or was better supported when that code was written)?
A quick check suggests that Linux, Windows, macOS and FreeBSD and OpenBSD support both variants, but I don’t know when they started supporting each.
According to NetBSD, Tru64 Unix, HP-UX11i only support _exit(), not _Exit() and IRIX supports neither.

UPDATE: Ok, maybe is a bit outdated, says that NetBSD supports _Exit() as well since NetBSD 2.0 (from 2004)

This is added, thanks!