What Motor Daddy appears to be saying is, that there is only one frame of reference.., that of the observer's (his), and that all other frames of reference including yours and mine are illusions, from his frame of reference.
The only thing that exists is that which lies within his box.., his frame of reference.
This is a valid point of view consistent with some frames of consciousness I have read about involving aboriginal perspectives, mostly from isolated Amazonian tribes... You know some who have no concept of numbers.., they give you half of what they have and they still have "all" of what they have left.., or those with a time sense that includes only today and three days into the past or future and those who believe only that which is in the experience of a living person is real, this later includes the dreams of living persons...
I think I finally get MD's perspective.., only reality as he sees it is REAL. Everything else is illusion or delusion. From there, there is no way for him to see the illusion or delusion, of his own ideas.
Sorry, I kind of digressed from the discussion of physics to an evaluation of the apparent psychology or abnormal psychology involved. There may even be some research study out there interested in exploring his Box, but it is most likely to be found in psychology or neuroscience.