Which incorrect claim, specifically, is an example of what you talk about?

p(death is defeated). Not p(death is defeated | civilization survives).

Death will lose more or less inevitably, under the condition that civilization survives (and death has no say in whether it does).

Yes, more or less. The most obvious cases where it wouldn't are

• If one of Robin's speculated Malthusian futures came to pass. Or
• If someone goes and creates a dystopian singularity. (For example, if a well intentioned AI researcher implements CEV<Humanity>, gives humanity what it wishes for and it turns out that humans are coherently extrapolatably as silly as Dumbledore.)