True. But addiction is addiction, whether it's psychological or physiological.
Sure, you can't have withdrawals from MDMA, but are withdrawals required for something to be considered an addiction?
I have a friend that takes MDMA at least twice a week. The depression is awful, and her tolerance is ridiculously high... but the slight euphoria she is still getting from it is enough for her to keep doing it. However, she is also addicted to the fact that it has made her lose a ton of weight.
It's totally normal to think about ecstasy and be excited to do it again, but when you're breaking promises to yourself.. such as "I'm going to wait ___ amount of time before I roll again" that is definitely a sign.