In a finite universe world there are no true turing machines, as there are no infinite tapes; thus if you are going to be assigning some philosophical heft to turing-completeness you are being a bit sloppy, and should be saying “show me something that provably cannot be computed by a finite state machine of any size”.
Why the hangup about turing-completeness?
In a finite universe world there are no true turing machines, as there are no infinite tapes; thus if you are going to be assigning some philosophical heft to turing-completeness you are being a bit sloppy, and should be saying “show me something that provably cannot be computed by a finite state machine of any size”.