It was already diagnosed by both the WHO's ICD and by the APA's DSM. In both it could be diagnosed as a compulsive behavior disorder. Many people with compulsive behavior about game playing have been diagnosed (and successfully treated!) under the diagnostic codes of compulsive behavior disorders or obsessive compulsive behavior disorders.
What changed is that now this is a specially enumerated compulsion. The nay-sayers who claim the behavior cannot be an actual disorder now have this against their argument. That includes nay-sayers in the insurance industry who are forced to accept it can be an issue.
People can have nearly any behavior become a compulsive behavior. People commonly think of excessive handwashing and aligning objects when they think of compulsions, but it can be any behavior at all. Having locked doors at home or thinking about the stove being on are common ones; many people have it trouble them during vacations and long trips, but a few people obsess over the ideas. Mothers repeatedly checking on children is common; most mothers think about their children, but for a few people the thoughts and behaviors interfere with their lives. Obsessive thoughts or compulsive actions about work or school classes is common. Risk-taking compulsions are common. None are considered a disorder until they start interfering with regular life. When someone hears about them it is easy enough for most people to realize this is not normal and needs help.
Most compulsive behaviors are never specified in a diagnosis, the person is merely diagnosed to have a compulsive behavior disorder or an obsessive compulsive disorder. Only a few specific behaviors have been specifically enumerated, in part because they are severe yet people don't think they are real health problems. Gambling was controversial when it was added as a named diagnosable item, and many common folk who didn't know better said that people couldn't be hooked on gambling, it was just a bad habit. Hoarding was also controversial when added, many common people struggle to understand that hoarding isn't just that the person doesn't want to throw stuff out, it is that they cannot get rid of things without psychological harm.
A kleptomaniac is another, they cannot stop from taking things even when they know it is wrong and even when they make a concerted effort to stop. They're not taking things because they want to, or because they covet the items, they are incapable of stopping themselves. Telling them not to steal doesn't help because they DO know better. Trying to explain it is wrong doesn't help because they ALREADY know it is wrong. Many times they don't like that aspect of their lives and they would change it if they could. It takes professional help to change the behavior. Relatively few people are affected by the condition and most thieves don't have it, but it is a true medical condition requiring professional help.
Sadly there are people who refuse to accept that certain behaviors are actually compulsive, that the person cannot help themselves and cannot stop themselves no matter how hard they try.
This affects all entertainment. Most common folk don't seem to understand that binge watching, or being a couch potato, or a lounge lizard, or even a gamer, for some people is not just about being lazy or choosing to play before getting the work done, or choosing to play late into the night. For some people it is a behavior they cannot stop, just like the person compelled to wash their hands. By specifically enumerating it, they're more likely to accept that some people can have it as an actual condition rather than "just being lazy".
Really, we spending more time looking to Visual Stidio windows, than bandits, looking to jail windows 
