How did Dorn survive being stabbed by the Pale Spear?

I’ve been going back over the text of Praetorian of Dorn and during the primarchs duel, the text specifically says “Dorn was stabbed through the armour and into the flesh.”

From everything I’ve read, seen and heard of the Pale Spear, it’s kind of a 1hit kill as it turns a person’s blood into a black smoke and so even a graze can be lethal. This point is reiterated a couple of times in the Harrowmaster book.

So, how did Dorn just shrug off this attack and no-diff it? I’m okay with Alpharius dying at this point in the story but it feels cheap if Dorn doesn’t have to like cut off an arm or something to stop himself from dying.

Another big gripe I have with this book is that there was no real consequences for the Loyalists. Like sure, the Pluto station is kinda fucked, but long-term, this is just a straight Alpha Legion L. It makes the story feel unnecessary because the “good guys” don’t take substantial losses and only lose a communications relay.