That was a nice test. I would assume the brand must have been Cobra.
One specific thing they mentioned is very true in my game with my SL set. On par 3's, the 5 iron is way better than a regular length one. 6 iron too. And my course has two par 3's that usually play as 5 iron for me. There is just enough extra height with the teed ball that I cannot complain about the flight.
But as they said, at my swing speed, if I need a high approach shot with a 5 iron, well, it ain't high enough. They talk about 4 iron too, but that's not in the cards for my speed.
There is something to the better impact quality in the 5 and 6 iron SL clubs too.
As to short irons, as I gained confidence with them, I would say there is not much loss of accuracy versus conventional shorter irons. Overall, I started out on the fence about the idea. But as I play them more, I think they are the way to go.
If a person is carrying only 7 iron and shorter now, then probably not. UNLESS it's because they just can't hit a normal 5 and 6. In that case, an SL set could get them back into irons, with probably much more accuracy than their hybrids.