We have this code with the comment:

// Workaround for a bug in macOSX kernel's pthread support (fixed in Mojave?).
// Avoid ever allocating a pthread_mutex_t at the same address as one of our
// former pthread_cond_t, by using freelists of mutexes and condvars.
// Conditional to avoid extra indirection and padding loss on other platforms.
#ifdef __APPLE__
#define PLATFORM_MONITOR_IMPL_INDIRECT 1
#else
#define PLATFORM_MONITOR_IMPL_INDIRECT 0
#endif

It is time to remove it.