Destruction of condition variable randomly loses notification

Given a condition_variable as a member of a class, my understanding is that:

1. The condition variable is destroyed after the class destructor completes.
2. Destruction of a condition variable does not need to wait for notifications to have been received.

In light of these expectations, my question is: why does the example code below randomly fail to notify a waiting thread?

#include <mutex>
#include <condition_variable>
#define NOTIFY_IN_DESTRUCTOR 

struct notify_on_delete {
    std::condition_variable cv;

    ~notify_on_delete() {
#ifdef NOTIFY_IN_DESTRUCTOR
        cv.notify_all();
#endif
    }
};

int main () {
    for (int trial = 0; trial < 10000; ++trial) {
        notify_on_delete* nod = new notify_on_delete();
        std::mutex flag;
        bool kill = false;

        std::thread run([nod, &flag, &kill] () {
            std::unique_lock<std::mutex> lock(flag);
            kill = true;
            nod->cv.wait(lock);
        });

        while(true) {
            std::unique_lock<std::mutex> lock(flag);
            if (!kill) continue;
#ifdef NOTIFY_IN_DESTRUCTOR
            delete nod;
#else
            nod->cv.notify_all();
#endif
            break;
        }
        run.join();
#ifndef NOTIFY_IN_DESTRUCTOR
        delete nod;
#endif
    }
    return 0;
}

In the code above, if NOTIFY_IN_DESTRUCTOR is not defined then the test will run to completion reliably. However, when NOTIFY_IN_DESTRUCTOR is defined the test will randomly hang (usually after a few thousand trials).

I am compiling using Apple Clang: Apple LLVM version 9.0.0 (clang-900.0.39.2) Target: x86_64-apple-darwin17.3.0 Thread model: posix C++14 specified, compiled with DEBUG flags set.