Perhaps an unusually strong staggering response as the plant enters flower? This would be my first guess, I've had a photo once or twice before that changed to staggered nodes in such a way that it looked like it had 2 main branches as if it had been topped. I did top both of them and got a really nice looking bush out of it. NGL, it could be other stuff like genetics too, just personally have experienced something similar once before as more or less "natural" growth, so its the first place my mind went!