Why don't calls to emergency numbers show in the Phone app's call log?

I recently had to make an emergency call. I later noticed in my device's call logs in the Phone app that the emergency number I called doesn't show up in the call log. (In other words, no entry shows of the call; no trace in the call log that I called an emergency number.) Why is this? Is this intentional and by design, or is it a bug? (Using stock Android 8.1 with latest updates on Nexus 6P.)