I speak about DT and MWI in terms of opening post, where they need to explain more general theory which was named "flux universe". Idea of flux universe is that things which are not inside your attention become blurred. The most well known example of blurred things us Shredinger cat. But in my opinion you do not need neither DT or MWI to get to flux reality. Because even in classical universe the same observers (copies) may exist in different circumstances. And if I deliberately exclude from my attention many things I will become equal to many other observers, thus changing size of my reference class.