It's simply part of a coordinated, multi-pronged attack on gaming. Really, there is nothing to be surprised about here. Every single avenue of attack that can be conceived of is being tried, if one or more of them succeeds in getting people to scream "oh please big goverment, take away my freedom, and protect the children!" it will be a success.
See, the problem with the logic here is that there are also studies that claim to show that the US is behind in terms of academics and other things, yet some of the countries that are kicking our can (allegedly) are much more heavily into gaming than the US. Japan and Korea both come to mind.... not that I entirely agree with these statistics either (for various reasons, which I have gone into before)... the point being that the same guys making this claim about how video games are hurting our kids in school are typically going to be the same guys who will argue about how countries with bigger gaming habits are outperforming us when they want to try and make another kind of statement.
A big part of the problem is that I don't think people really understand ADD and ADHD very well. It became a hip diagnosis for a while to present the illusion of medical professionals doing something. In the end this lead to some people who got strict with kids and pretty much shoved a boot up their butts getting them to change, leading a lot of people to believe that these conditions can be dealt with the same way. There is a differance between a kid with ADD or ADHD and a kid who is just being lazy/a jerk/slacking off... typical non-medical problem kid stuff.
The thing about ADD and ADHD is that it causes trouble focusing on things even when the victim in question wants to. Things like TV and Video Games don't cause ADD and ADHD, but can get people with those types of problems involved with them because of the way the content works and that it can rapidly change.
ADD and ADHD are an inherant condition, not something that you catch. I'm a sufferer and got mine from brain damage. One of the ways to tell if someone is really afflicted with one of these conditions or if a doctor is BSing you, is to look at what the person in question has tried to do. A real ADD or ADHD sufferer probably has tried to do a lot of differant things (that can involve anything from taking Karate Lessons, to trying to play an insturment, or similar things) and then ultimatly failed because despite their interest they just couldn't remain focused on it. A regular person who wants to try something like that can force themselves to focus to make an effort, even if they wind up failing. An ADD or ADHD person generally can't, indeed when a person with these conditions tries to force themselves to focus on such things they tend to get tired since literally their body will try and shut itself down/knock itself out than try and stay unsuccessfully focused.
Basically what I'm getting at is that a lot of ADD, ADHD sufferers lose themselves in things like TV and computers because content moving at that speed and with that much changing stimulus is something they can enjoy. After a while people with these conditions just figure "F@ck it" and stop caring about other things, which can bother people (especially parents) who sometimes wind up banging their heads into walls in frustration because they aren't trying any more.
As I said, I've been there and I'm currently able to articulate thoughts on the subject that I don't think many kids can.
Also depending on severity, when looking at an ADD/ADHD gamer, you might very well find that he/she moves around between dozens of games (usually a very expensive habit for people like this) and rarely finishes them, compared to many people who play a game from start to finish. That's a sign of a really serious problem, since the person in question is having trouble even staying focused on that form of escapism. When it comes to TV, in really bad cases it leads to compulsive channel surfing and such.