I had a few runover this year by the lawnmower, a few of them acted as if they were topped and started growing again with double stalks. This giant hybrid I'm growing this year took a long time to get started but they're tough as nails now. I had never grown any that made multiple flowers all along the stalk. The bagseed ones I always grew only made a single flower but still got 6ft+.
Also I have one little guy that just sprouted about a week ago who has double stalk all the way from seed, never seen this before on a sunflower.