One can only surmise his philosophy denies relevance of these topics in his treatise. His adapted Popperian philosophy appears to contravene relevant artifacts of orthodox Copenhagen quantum theory. I think a unification of Deutsch's ideas and selected Copenhagen concepts which he dismisses are superior to either alone. They revise their experiment to only permit successive incremental delivery of unit photons to traverse both slits. However, a familiar interference fringe pattern integrates gradually with each new photon's traversal.
Analytical things are incapable of depicting quantum reality.
All of this argues against an object model capable of interference with itself or, as Deutsch suggests, another multiversal object. See our review of Irving Stein's, The Concept of Object as the Foundation of Physics . Yet Deutsch tells us that an individual photon, as an objective particle, cannot interfere with itself, but somehow it can interfere with other objective photons both in a local multiverse and in nonlocal multiverses. In our opinion, objectivism is a paralytic disease of otherwise great minds.