Regarding the parallel lines, it does seem clear that the VM uses the motif throughout for various purposes, so it needn't always mean the same thing. Sometimes it may even be ambiguous by design.
Here are two clips from f75r:
The one on the right does show something close to what you have in mind, but not entirely. The parallel lines are marked by a border where they touch the land, so we see clearly what's going on. Additionally, the pattern seems to be intended to represent the "cliff" surface with some depth, so we know the water is lower than the land. Look at the whole puddle on You are not allowed to view links. Register or Login to view. and you will see that it is not quite like the mapmakers' shorelines.
On the rosettes page, too, we see parallel lines used to represent cliffsides, but also other things. The pink arrow points to cliffside usage, the rest seems to radiate from the scallops, without a pen line to denote any land border.
That's all I got though. If you still think that what I say makes no sense, you will automatically win the discussion.
Here are two clips from f75r:
The one on the right does show something close to what you have in mind, but not entirely. The parallel lines are marked by a border where they touch the land, so we see clearly what's going on. Additionally, the pattern seems to be intended to represent the "cliff" surface with some depth, so we know the water is lower than the land. Look at the whole puddle on You are not allowed to view links. Register or Login to view. and you will see that it is not quite like the mapmakers' shorelines.
On the rosettes page, too, we see parallel lines used to represent cliffsides, but also other things. The pink arrow points to cliffside usage, the rest seems to radiate from the scallops, without a pen line to denote any land border.
That's all I got though. If you still think that what I say makes no sense, you will automatically win the discussion.