Addicts will say absolutely anything. I am sure he does mean it, but when the rubber hits the road, can he stay clean? Likely not.
Tell him to talk to you again after he has been clean for at least two years. AFTER, not before. That is where you will see truth. It's all about actions, not words. I caution you about the "rock bottom" theory. Many don't have a bottom. Addiction ebbs and flows, and can do so for many, many years.
He is not your responsibility. If we could love them clean, none of us would be here in the first place.