Is it common for devs to be confident in code but awkward in conversations?

Depends. Am I talking to another dev? We can be very confident, making very precise statements, disagreeing at times but each convincing the other when we are right, because there is an objective truth and we're both evaluating arguments on that basis.

Or am I talking to someone at a party about, say, modern art, or politics? Yeah, there may be some awkwardness, because they don't talk the way we talk.

Not sure if I fully qualify as a dev but I, for one, are rather confident in conversation. But with code, there is only two modes: Either I am the biggest idiot whoever disgraced Earth's surface or I am the absolute titanic Übergod for whom no problem is too hard to solve. There is nothing in between which is pretty vexing.

Yes