One more note on context — there’s a common context flags can appear on that you haven’t covered, and that’s appearing on paper or other white backgrounds. Scroll up to the large images near the top of this article and you can see that both the koru and the black and white fern would need an outline to convey their rectangular shape. Red peak also suffers this problem, though only along 2 quarters of one edge.
I do think you’ve been a bit harsh on the black and white fern in the symmetry section. It may not be symmetrical in the literal sense, but at a glance it does read as a very symmetrical design, within the shape of the fern.