Whatever the piece assumes, I don't think it's preference utilitarianism because then the first sentence doesn't make sense:

In total utilitarianism, it is a morally neutral act to kill someone (in a painless and unexpected manner) and creating/giving birth to another being of comparable happiness.

Assuming most people have a preference to go on living, as well as various other preferences for the future, then killing them would violate all these preferences, and simply creating a new, equally happy being would still leave you with less overall utility, because all the unsatisfied preferences count negatively. (Or is there a version of preference utilitarianism where unsatisfied preferences don't count negatively?) The being would have to be substantially happier, or you'd need a lot more beings to make up for the unsatisfied preferences caused by the killing. Unless we're talking about beings that live "in the moment", where their preferences correspond to momentary hedonism.

Peter Singer wrote a chapter on killing and replaceability in Practical Ethics. His view is prior-existence, not total preference utilitarianism, but the points on replaceability apply to both.