I don’t really understand what you are trying to say?

Are you are trying to say that he will not get paid for time that he is not at work?
If this is indeed what you are trying to infer than it all depends. If his “pseudo-boss” is cool and wouldn’t mind (or more likely really doesn’t care) if he took off for the day because he has nothing to do than its all good. Your boss should know better than anyone that coworkers get pissed when they are working and others who are getting paid aren’t. Better for him if you were not there. However if his boss is the type to make him stay even though he doesn’t have anything to do than he needs to accept the consequences of his instruction. I wouldn’t worry too much about getting caught playing games or browsing the Internet.

Or are you trying to say that he gets paid for doing nothing?
A lot of people get paid for doing nothing. In fact when you start making a lot of money you generally get paid for what you know and not what you do. If the shit hits the fan you need to know your shit or your ass is gone. But when it’s slow and nothings going on its generally known that you aren’t doing much.