It has to work on both levels of meaning. A ship's mast cannot be wrapped around a body like a serpent. Hence it is
evoked by the way his arm is drawn. I know you don't like that word, but one cannot analyze all levels of art without it. An obelisk might be said to evoke the shape of a phallus. That is a valid observation, whether the resemblance is intentional or not.
Here I'm presenting some random examples, but if you check the recent posts on my blog you'll see that the elements aren't taken out of context at all. I analyze a whole folio and the constellations are clustered and in order.
I don't see why you formulate such a strong statement that I arbitrarily interpret repeated motifs. It has been discussed ad nauseam here that wavy lines represent boundaries between (heavenly) realms. So this is a perfect motif for representing the ever visible circle, which was considered the "true" heaven in astronomy, because it never dips beneath the ocean.
Can't possibly apply to any other cases? Why do you say that? Some examples:
Draco sits above the line, Bootes beneath it:
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The two ladies on top of the same folio are placed on
two layers of wavy lines, because the theme of this myth is how Callisto became placed at the pinnacle of the heavens. The Ursae obviously sit above the pole circle.
I haven't analyzed this folio yet (that takes way more work and time and research than you seem to imagine) but this figure is clearly Cassiopeia. This has even been suggested by people before me. She touches the line with her feet:
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