He responded by saying rehab is not what he needs. He specifically said "They can only teach me what I already know. There isn't anything about recovery that you can teach me. What I've always lacked is the will to make the step/effort to change. That is something I have to do on my own,
He's right about this. Rehab is not a factory that spits out recovered addicts. The main ingredient in any sober plan is willingness to do whatever it takes. That is something the addict can achieve with or without rehab. There are many, many recovering addicts on this forum who never went to rehab.
and I'm more ready than I've ever been.
This sounds hopeful, but again, it is up to him whether he holds onto this thought. His plan may not be what you would hope for, but it's his plan and he really needs to do this in his own way.