We went through this "rope" superstition on another thread. In traditional seamanship, a rope is a rope, a very heavy and stout rope in a particular application may be a "cable" or a "sheet" or a "brace" or a "shroud." A light rope is a "line." A real sailor would automatically use the most appropriate term, but "rope" was still generic.

Small ketches, e.g., have "lines." If 20th C. naval usage requires "line" for any kind of rope, it's a recent development.