According to
this very interesting article, it is indeed.
Well, there's not much there to really go on. What is there seems to suggest transition difficulties, which makes sense because the new S-LSA have different flight and control characteristics from either fat ultralights or Part 23 airplanes. It's also significant that they noted a lower accident rate among pilots whose training was in LSA.
I have to be honest, as someone who's flown several new S-LSA models... I think too much is being compromised to make new S-LSA look and feel like "real" airplanes while staying within the LSA weight limit. I'm not aware of any of them that are intentionally spinnable, for example. That's why I chose to do spin training in a Cub. None of the LSA at the FBO were spinabble.
The article mentioned loss of control and structural failure as factoring into the accident rates, and I really believe that's more a function of the weight limit than anything else. I don't want to call these aircraft flimsy, but... well, some of them feel flimsy to me.
I also don't completely buy the "inferior training" hypothesis except inasmuch as the standards weren't developed with the current crop of S-LSA in mind. I particularly dislike the fact that so many of them have glass cockpits. I'll admit that I personally dislike glass anyway, so there's some prejudice there; but I also think that learning to use and interpret the instrumentation is not something FAA had in mind when they came up with the training standards.
That doesn't make glass "bad," but I don't think anyone would disagree that it does make for another set of learning tasks; and I seriously doubt that FAA factored that set of tasks into the standards.
On a more personal, "hunch" sort of level, I also think that the less instrumentation an airplane has, the better it is for early primary training, when the "feel" factor of flying is being learned. If I had my way, every student would have to have some time in a Cub, Champ, or something along those lines (or one of the LSA from the fat ultralight heritage), for that reason.
Then again, more and more ultralights nowadays have a Dynon EFIS, so maybe I'm letting my prejudices get in the way.
-Rich
EDIT: Just to be clear, I don't believe that raising the weight limit would necessarily help very much. I suspect manufacturers would use most of that extra weight for more bells and whistles and creature comforts than for any meaningful improvements in structural integrity or flight characteristics.