When the body's homeostasis is sufficiently disrupted, there is a compensatory response to bring the body back to homeostasis. This is what causes most types of drug tolerances and plays a significant role in addiction. For example, if someone takes cocaine for a period of time, that person's body will begin to compensate for the euphoria caused by the cocaine by creating a sense of dysphoria, which forces the person to take more cocaine to get the same effect.
It turns out that this compensatory response can be conditioned using classical conditioning. For example, if a bell is rung every time before a person takes cocaine, then after a while, just hearing the sound of the bell will trigger the compensatory response and make the person experience dysphoria. That means the person exposed to the conditioned stimulus will have to take some cocaine just to return to their normal baseline level.
If the claim about video games being addicting is true then first of all, it would have to mean that video games can disrupt the body's homeostasis enough to create a compensatory response. Second, there would have to be a conditioned compensatory response since the environment where the person plays the video game will become the conditioned stimulus. That means you can test this hypothesis by have a control group that does nothing in a controlled environment and an experimental group that plays games in that same environment. After a period of time, you test to see if the experimental group has developed a conditioned compensatory response compared to the control group based on physiological and mental changes in response to the environment. Without any experimental data to back up these kinds of claims then they're completely meaningless. All this therapist is doing is undermining psychology as a science.