He (probably) needs IC for a couple of other reasons.He does NOT need IC to uphold his boundaries of a marital union.
In my own experience, more than a decade of having my emotional needs neglected (including sex-related ones) or looked down upon, and after being rejected (sexually and otherwise) so many times I now reject myself on her behalf, I realize it has all greatly affected me. I have been depressed. Very. And, though at some time in the distant path I could maintain an independent perspective on reality, I find it hard at times not to FEEL as if the sh!tty way she treats me is what I deserve. Ultimately, that effects how I relate to my wife, which feeds back into how she relates to me.
It's not that I cross her boundaries, it's that I don't effectively declare and enforce mine.
My hunch is he may be dealing with the same sort of fallout from those many many years. IC is helping me get healthier, psychologically. That in turn is forcing my wife to have to face more of her demons on her own. I'm hoping OP will see a similar change occur.