Most people bullshit at parties, either by embellishing or by exaggeration. It might not always be about their profession but it is a storytelling technique to make their story more interesting.
It's a poor indicator I'd argue.
I don’t know about “everybody”. It depends on your circle I guess. I know very few of these people and none of my friends are like that. I don’t give a shit about being interesting and nobody I value does either.
Many do, but not most. At least not at the parties I attend. And in my experience, it is a strong indicator. Some might manage, to vent out everything BS at parties, but for most their general attitude about appreciation for truth will show in a private setting just as it will show in a professional one. In the professional setting people just care more about hiding that BS.