tl;dr: Yes, with the small language tweak that I recommended, this looks good to me.
Agreed. Zero complaints! Sounds like a win.
No! It didn’t. (!) I only sort-of noticed that the sites weren’t coming up before I did the second stage of the install that enables https. And my setup isn’t your responsibility. (Oh, NOW it’ll break my script, but not doing the installation before DNS is set up will be better anyway. I haven’t done a non-https installation in at least a year.)
The reason that I liked having my script use discourse-setup is that it makes extra-special sure that my install customers are getting a Standard Install, and that when someone says “I did an install and it didn’t work” I can run my script and do exactly what they should have done and say “Well, I just did an install and it worked.” But I don’t think I remember a time in the past 3 years that I found an issue, so perhaps my “testing” isn’t doing anyone any good.