It's not bravado. If a road is too narrow to be safely passed, you need to either take the lane, or not be on that road.

For example, I was driving today down some rural roads (1 lane in each direction) with no shoulder. One of the cyclists was riding right on the fog line, because there was no room to the right. I hesitated, and wondered when to pass. I ended up passing carefully after all was clear, because I wanted to be careful. However, I never could tell from the cyclist if it would have been ok to pass sooner. I noticed the other drivers passed him much more closely and quickly than me.

If he had been a foot or two out, or gave me some don't pass/go ahead signals, I would have felt much more comfortable with the situation. It's tough that there is no bike lane or shoulder, but riding on the fog line is not necessarily a safety improvement. I personally would not enjoy riding on that type of road at all, in case you were wondering.