What exactly do you mean by "principled"? It sounds loaded, but I want to give you the benefit of the doubt and not make assumptions.
Principled as in following the principles of good GMing in the handbook (such as in Dolmenwood the outline of a Referee’s Role, how to Describe the World so that players have sufficient info to make informed decisions, and where the players are given concrete guidelines on how to execute procedures). In the case of some NSR games like His Majesty the Worm, the book contains some best practices and further refers out to community blogs for further details.
Edit: the latter specifically commends the Principia Apocrypha to referees/GMs, which clearly states the principles there in as “rules GMs should follow supplementary to the game’s rules… to guide you when what you should do is uncertain.”