Are you sure this isn't placebo effect? I.e. you've always had this capacity, but the reason you're having success is because you're now focused on utilizing it. That's somewhat different from not having the capacity in the first place.
I can say that I've tried, and have a real problem with similar exercises.. that said, I don't learn the same way a lot of other seem to. I am pretty good at getting a couple dozen things into my head at once, but my mind tends to wander beyond that point and I will lose focus.
In some ways this works to my advantage, in general an application or system I am working on can fit mostly in what I am actively thinking of at a given time.. the down side is I will then lose track of time, and side thoughts... it will be 7-8-9 at night, and I'll stop because I need to use the restroom, realize how late it is and that I'm hungry.
On the flip side, I rarely misplace things, I have a photographic memory, not eidetic... In general if I write something and see it at the same time, I'll remember.. if I only see it, it depends, and if I only hear it, I'll likely forget.
I do most of the things mentioned in the article regularly though... I've managed to cope pretty well with my advantages and disadvantages.
