Isn't it like saying the human body is a PC which has inputs (ports) and outputs (display, sounds) and the brain is like a CPU which has its own inputs and outputs? and you can always go further i.e the transistors have their own inputs and outputs
If that's what is meant by 'an input/output mechanism' then it seems like a pointless observation. It's just saying "you can do things to it, and you can observe things about it", which is true of pretty much anything.
The problem is we don't know all the inputs, and there is much hidden state that we can't observe. So it isn't very useful to try and model a human after how a computer works.