It's just semantics. What they mean is that it's not classical addiction in the sense that players are not chemically or physically addicted to gaming. As in, if they stop, they don't start vomiting and convulsing. They use it as a form of escape and begin to rely on it in order to avoid real life so they play all the time. So it's related to a social disorder, not a true addiction.

People like Oprah and "Dr." Phil call it addiction in the media because it's a stronger term and they really don't know what they're talking about.