And "Parallels" reminds us that everything you've written and that we've read "really" happened. Somewhere in Trek's multiverse...
Which is exactly why I've never had an issue with the differing views of the "Mirror" universe from the DSN episodes, the Enterprise episodes, the DC comics sequels, Diane Duane's novel Dark Mirror, and David Mack's MU books. They all happened, just in slightly differing versions of the MU.