I had a gigabit fiber-to-the-home connection in an area inside of Denver city limits (more than 3 years ago by the way) that is not shown on your linked map, so your data source for this is not accurate.
Oh I see. That's actually a map of where they are currently _expanding into_, not where they offer service. A much larger part of the city is covered than what that map is showing.
The parent comment is a better reflection of the state of CL's fiber rollout than you might think. I recently did the exercise of trying to figure out what homes did and didn't have fiber from them all around Denver.