[1] Sometimes I still marvel about how in most time-travel stories nobody thinks of this. I guess it really is true that only people who are sensitized to 'thinking about existential risk' even notice when a world ends, or when billions of people are extinguished and replaced by slightly different versions of themselves. But then almost nobody will notice that sort of thing inside their fiction if the characters all act like it's okay.)

I think that's because people change into their analog in the new timeline, rather than disappearing in a butterfly effect - the resulting person is still "the same person", and thus they have not died (much like we don't conclude people have dies when we cut to "twenty years later" and they all have grey hair.) Unless, that is, the intent was to "kill them in the past", in which case it's treated as murder, or time travel is A Bad Thing, in which case it's sometimes inevitable that meddling with it results in people never being born and that's terrible.

Although the characters being fine with it all doesn't hurt, either ...