Not a stable strain, not a true autoflower. Some of the phenos will autoflower while others will not. A true autoflower would not be clonable and would not revert back into veg, which short rider can. Some of the phenos are autoflower and some of them, regardless of auto or not, are just horrible. Not the most impressive stuff and, in my humble opinion, there is a reason why its on sale. It does however grow quite bushy and is suitable for growing wide short plants. It has its uses, but if you want consistency or something amazing, this is not the strain to buy.
Sorry guys.
Also, im fairly confident that when you switch back from 12/12 to try and use a longer light period, many times the short rider will stall and start vegging again. You may get lucky, but from what ive SEEN and of course read, I would bet against you actually getting what you want out of this plant.