That may be so, still I don't hate the trope at all if they have fun doing it haha. There must be a trigger for ascension anyway, might as well be the "sound" logic of poisons inhibiting each other.
I'm really enjoying this series so far, its great!
I looked it up and found a study of an autopsy where tetrodotoxin and aconitine counteracted each other, delaying death significantly. Seems like this is legit, the supernatural martial arts do the rest of the work.