Well, sort of, but I still think there is an important difference in that without big world immortality all the survival scenarios may be so unlikely that they aren't worthy of serious consideration, whereas with it one is guaranteed to experience survival, and the likelihood of experiencing certain types of survival becomes important.

Let's suppose you're in a situation where you can sacrifice yourself to save someone you care about, and there's a very, very big chance that if you do so, you die, but a very, very small chance that you end up alive but crippled, but the crippled scenarios form the vast majority of the scenarios in which you survive. Wouldn't your choice depend at least to some degree on whether you expect to experience survival no matter what, or not?