i said still arguable because the wiki says that we can save Cliff if we rush quick enough to save Jenny (in the quest page).
i don't think this is true, at least maybe not anymore.
i stealthed to get past Cliff and get inside the trap door, in order to clear the area from burrowers and opened the necessary ventilation shafts to ensure i can rush to Jenny as fast as i can after i start the quest.
then i get out to talk to Cliff to start the quest, get in the trap door instantly after the convo ends, then rushed to Jenny very easily with all burrowers dead and ventilation shafts opened, but Cliff STILL dies.
the ONLY legal way to save him is to save Jenny without starting the quest, but that means you don't get any XP or oddity XP.
this is even more interesting : after i started the quest by talking to Cliff, i went inside the trap door, then instantly went back out again, and Cliff dies even though it's only about 1-2 seconds passed and the bleeding still needs way more time to completely kill him (counting by the bleeding damage and his remaining HP).
i think the quest page on the wiki needs to be updated, unless there's something i missed. (my game version is 1.1.1.3)