Earlier quoted context omitted.
On my map it seemed like the road consisted of a few points, rather than the points plus lines between them (or however it's described). Selecting intersections (maybe bends?) lowered the distance.
Yes this is something I need to fix. I think you're right. I think it's measuring to the nearest node on the road (in the OpenStreetMap data) and not every point on the line as we see it. It could be related to the fact that some roads are actually broken up into multiple with the same name, not sure
This is fixed now!