Firstly, I'm very impressed by your scoring. Well done. I'm jealous !!!
From a philosophical point of view, I personally would not count this as a "true" 66 if I were in your cleats. Everybody knows it's easier to maintain a better performance for a shorter stretch than for the full 18 holes. It's part of what keeps us coming back. We look at stretches of play that demonstrates our ideal performance. Our score improves as we extend those stretches longer and longer, until we make it all 18 holes.
But, like I said, VERY well done nonetheless.
