I think the problem stem from the author’s definition of computation. He has defined it around the state of a Turing machine, which is vastly insufficient.
The important part of a Turing machine is that of the behavior: given a certain state, the next state is a result of the current instruction on the tape.
It is easy to imagine identifying some mapping from a Turing machine state and an iron bar. However, mapping the next state to a valid state transition of the same Turing machine seems quite unlikely, graduating to impossible, as the Turing machine executed.
Said another way, a program is not its memory dump.
The important part of a Turing machine is that of the behavior: given a certain state, the next state is a result of the current instruction on the tape.
It is easy to imagine identifying some mapping from a Turing machine state and an iron bar. However, mapping the next state to a valid state transition of the same Turing machine seems quite unlikely, graduating to impossible, as the Turing machine executed.
Said another way, a program is not its memory dump.