The thought experiment is about eliciting some of the normative content of truth vs. falsity of MWI, in terms that don't assume MWI.

That is not my reading. Consider this part:

If you treat quantum measure squared exactly as probability, then you shouldn't see any reason to replace the trigger. But if you believed in many worlds quantum mechanics (or think that MWI is possibly correct with non-zero probability), you might be tempted to accept the deal - after all, everyone will survive in one branch.

The post then goes on to argue that there is a dilemma here, that an apparently plausible case can be made for either choice, assuming that MWI is true.

I take the post to be saying, "Here's an interesting dilemma. Well, it's only interesting if there's a possibility that MWI is true. That is, if you know that MWI is false, then the answer is obvious. But, granting the possibility of MWI for the sake of argument, what would you do?"