You are right that the mine passages part is just a goof on the maze in Adventure. Likewise, asking or telling the skeleton about something is a single-joke response; the statue is the only one that has varied responses. I would encourage you to ask the statue about lots of topics, and tell me if there are any you can think of for which there should be better answers.
I've thought for a long time about the exit portal in the Great Altar; I was influenced by Doug Egan's Afflicted and similar games where you can just leave at any time, should you want to. I'm still learning about good puzzle design, so I'll have to think about how to make puzzles for my next game that are both satisfying and fit with my conception of how the story should play out.