Oh dear. I think I have many, many black skirts. Like 15, I think? These are the ones I can remember off the top of my head:
Jersey maxi length, a heavy knit pencil skirt, a semi-flouncy one with a kind of chiffon overlay that matches my suit jacket, a pleated one in a heavy woven fabric, an a-line one, a couple of pencil types with slightly different pin stripes, I think I still have a midi-length mermaid-esque one with hot pink pin stripes, a light cotton one with silver embroidery and little mirrors (sort of boho/Indian style), a close fitting ankle-length jersey with a long slit in the front, a stretchy flared one, an a-line made from an odd raincoat-like fabric with white contrast stitching, and a corduroy mini. And I have at least 5 dresses that are black or mostly black.
Did I mention that I wear jeans almost every day...?
At any rate I think it's totally acceptable to have two very similar skirts in rather different fabrics. If you have several flouncy skirts then it is clearly a style that you like and that works for you, so to me it makes total sense to have different versions for different occasions.