This is why it is said that there are people that due to their genetic inheritance are more likely to become addicts, the reward system on your brain, aka dopamine, will reward you with some dopamine after a win, however in most people that reward will be on the small side and this will allow you to stop whenever you want, however for some people the reward will be so stimulant that they will keep gambling just to experiment that feeling again, regardless of the consequences this behavior may have on their finances.
I haven't heard that before, but the explanation you gave is the truth. There are some gamblers who can just walk away the moment they have won a large amount or the moment they lose all their budget. Although it's difficult to just leave, some people have a strong self discipline to obey their decisions at any time.