I think it's a normal response, given his history with this particular woman.
That said, it wasn't about a particular woman. It was about something in him--something that needs to be identified so that different coping mechanisms can be substituted.
I don't know what that "something" is. That's something for him to explore in IC. It's really important that it not be minimized or rugswept, because that ups the odds of another affair astronomically.
I'm not suggesting that your approach is wrong. But it is naive to believe this was about one magical woman. It was about a confluence of things, for which he gave himself permission to break his wedding vows.
He needs to figure out what these things are, AND gather new tools---so that if the stars align similarly again, destructive extramarital affairs will NOT be his way of dealing with things.
Millions of hugs to you.