If that dog spawned it's probably a bug. Nothing should spawn with <SpawnRating>-1</SpawnRating> afaik.
That monster hut looks cool, maybe they activated the various monster lairs in Coremonstergoodiehuts.xml. If that is the case, then there is a potential bug there as well. We've been using them in mods, and one of the downsides is if you Autoresolve the battle with the monster, you can't loot the goodiehut until you save and reload the gamemap. Has that been fixed?
Edit: Another problem with that type of goodiehut was dislocating the monster from the lair. Even if it was set to not wander, using Whirlwind to blow up the army would send it rampaging, and so would LOSING THE BATTLE for the goodiehut.