Do you think that the original SC helps as much? You have to do a lot of "clickfesting" in SC1, which you're spared from doing in SC2. Which means much more thinking in SC2. Wow.
I don't know. I never cared to get good at SC. With SC2 I actually practiced and tried to get better. But your intuition makes sense to me, and I want to agree.
I've run across a couple of questions about the value of dual n-back, and this is the best place I know of to find people who've worked with it.
If you've tried it, has it noticeably improved your working memory? Was it enough to be worth the time?