After updating my SamrtWatch I can confirm that “OK Google” works. My watch is now on version 184.108.40.206 and the Wear OS app is on 220.127.116.118809240. If you'd like to check for these updates, open Google Play on your Wear OS watches and tap on the “My Apps” button. If updates are available, they'll be right at the top of that section.
To check if “OK Google” is working on your watch, remember first to turn the option on and make sure your watch is awake before activating the command. To make sure “OK Google” is activated, head into your watch's settings, then Personalization, and tap the option for “‘OK Google' detection.”