When sailors refer to a rope as a line, are they also signaling that they're part of a monoculture? Or do they just need more specific terms than regular English (there are several words for various kinds of ropes: sheet, hawser, painter, ...).

It seems natural for professions to develop some specialized language. It's obviously a liability to not understand it, because you won't know what people mean. But it's not much of a liability not to use it if there is an equally precise non-jargon term.