Fluidly using the right jargon, and signaling that you 'know stuff' without sounding like you're trying hard too show that you know stuff, requires a fair amount of intelligence. (Incidentally, an inability to maintain a natural flow of conversation when someone knows a lot of stuff is one way highly intelligent people reveal that their social acuity is not that high. Their IQ may be extremely high, but a five minute interview can often easily identify these things.)

A certain degree of being articulate and appropriately assertive can be trained – I think I see this happen in the military. However, I don't think it's a fake signal, I think this training really results in greater general intelligence, or greater ability to succeed in any case.