I enjoy very much the GM Guide beta, especially all the random tables (I love me some random tables!).
However, I was surprised by the advice given on p9 about not letting PCs kill major NPCs easily. Especially "Even if they suffer a mortal wound there's probably someone to heal them nearby". That's contrary to most GM advice I've seen in modern games and surprising for a gritty sandbox game like Forbidden Lands. I've seen and heard my fair share of tales of players complaining that their GM gave the villain "invulnerable plot armor" because they had a cool plan for them. To me, that goes against both immersion and player agency, and I'm afraid that this kind of advice will encourage railroady GMs.
I tend to play by "Game of Thrones rules": anyone can die, regardless of how important they are to the story. The plot adapts, GMing is more fun when you're surprised, and it makes player actions more meaningful. Or, as Vincent Baker puts it in Apocalypse World: "Look at all your NPCs through crosshairs".
But maybe that's just me though. What's your opinion on that? Should the GM arbitrarily "save" major NPCs?