"Addiction necessitates a physical reliance on a substance that might even put the person at risk for death when not indulging(like with heavy alcoholics) which isn't in quite the same category as neurotically wanking it to Pornhub."

That's not accurate. "Addiction" (which is an overused and overbroad term) does not necessitate physical reliance. Indeed, physical reliance/dependence and addiction are completely separate issues.

Be that as it may, there is absolutely a physical reliance, and tolerance, that develops in people with behavioral addictions, who essentially "get high", and withdraw from the lack of, the intense stimuli their behavior provokes.

As for the symptoms of withdrawal, they are absolutely real and widely reported.