You seem like a person that has never had to deal with someone that is incapable of saying "I don't know." It is incredibly frustrating to project manage a team like that. It is tantamount to lying.
Sure I have - and like I said - it's easy to read this behavior from simply having a normal (but let's just say slightly inquisitive) conversation with someone. In fact even in recent memory I can think of multiple occasions where this behavior has emerged, simply when trying to get to the bottom of routine technical matter.