I think you're spot on in your assessment. I don't think he based his assessment on Jodi's lie so much as he based it on what he himself wanted it to be.
Don't get me wrong - I believe Jodi gave him the ball and he picked it up and ran with it...but I think he was already hoping it would be PTSD (or something similar) because he wanted a defensive defense iykwim. Without one there's really little he could have testified to, if anything. It's in his best interests too for something to be so broken within Jodi she's not fully culpable of her actions.
For me, and I'm likely very biased myself, this transcends unprofessional conduct, carelessness, or even just a partial evaluation and goes straight into red hot danger zone. When you have a professional disregard testing protocols, then disregard the assessments altogether, accept deceit in turn without qualifying his opinion, and completely disregard symptomology consistent with a whole host of disorders - including cluster B personality disorders - and that opinion, and testimony, could free someone who is quite likely, imo, to kill again...
I guess it becomes a perverse, nightmarish scenario altogether for me. It's doctors like him who should be pledged to protecting people like us from creatures like her - not the other way around.
But that's JMO.