I don't think it's a race condition for two reasons: adding a `time.sleep(1)` after `.start` still raises errors, and in issue37193, there were 10 threads created, with at least 9 of those reaching termination before the test ended, yet it showed 10 reference leaks.

If you join the thread in the test, the leak is not detected. However, I believe that's because, in order to join on the thread, you must also hold a handle to the thread, so the condition isn't triggered.