In the universe, everything boils down to physics. Even the most complex human behaviors could be justified if we understood the physical complexity of the brain. But we can't, so we just refer to that complex behavioral layer of humans as "psyche".

Some people could become addicted to a substance because it makes them feel assertive, so they feel insecure while they aren't under its influence. How do you explain that physically? "Feeling insecure" belongs to the complex human behavioral layer. This would be a valid psychological addiction.

Everything is physical in the universe but we still have psychological disorders.

But, I agree, what most stoners call "psychological addiction" is just physical abstinence. It's just crap like "I can't focus if I don't smoke". Well, yeha, your dopamine levels are all fucked up, dude.