Thanks for the clarification!
The only option I can find is the "Death and birth" one, which seems to not do anything as regards to companions.
Not sure this is the one you refer to but I can't seem to find the "old" option either in Campaign mode or the new Sandbox mode.
It's good to hear it's a bug though.
I don't really mind there being a chance for my companions to die but it was happening so often I was starting to wonder why companions were even in the game still as a regular peasant seemed to have a bigger chance of survival.
I think I'll try just giving them a bow and a looooot of ammo so they avoid melee combat as much as possible for now.
So I just returned to Bannerlord after an 8-ish month hiatus and I seem to no longer be able to play with Resident Evil Protagonist style plot armor.
In all seriousness, I noticed there is no longer an option to disable hero death at the start of the campaign, instead it is now called...