you let an external agent inspect everything you do (while you inspect them) and where your incentive is to deceive them; where there is an asymmetry between your control of the environment, your lost effort, and your risk of espionage (and vice versa for them)
both of you observe the construction of a third agent on neutral ground where both parties have equally low control of the environment, low lost effort, and low risk of espionage (except for the coordination technology, which you probably want to reveal).
To me, there seems to be a big difference between
you let an external agent inspect everything you do (while you inspect them) and where your incentive is to deceive them; where there is an asymmetry between your control of the environment, your lost effort, and your risk of espionage (and vice versa for them)
both of you observe the construction of a third agent on neutral ground where both parties have equally low control of the environment, low lost effort, and low risk of espionage (except for the coordination technology, which you probably want to reveal).