Works for me. But I believe an update has changed it a little... When I first got my Note 8 I was able to say 'OK Google' and the assistant would immediately pop up and take my input bypassing having to get through security first but not anymore.
Before, I could take the phone out of my pocket, locked, and say "OK google, and when I feel the vibration feedback to indicate it activated, I could immediately say something like, "Directions to Ft. Lauderdale Airport" and it will bring up directions result on Google Assistant.
Now, when the phone is locked, I can say google assistant and I'll get the vibration, but goes straight retina scan so I already have the phone at eye level and then it goes to Google Assistant. But the mic is still hot so once I see the Assistant, I can then say whatever I want it to do.
So long story short, it works.