I don't think anyone with the Oreo beta has received the security update. No bug fix test updates either so it must either mean that the RTM release is imminent or there are so many bugs, they can't fix them.
I'm not going to hold my breath for any answer though.
While I'm happy overall with my Nokia 6, my next phone will not be another Nokia. The Nokia of old that produced the best phones on the world is dead. People need to remember that this is a brand new upstart company that is licencing the name. IT IS NOT THE REAL NOKIA.