Unless there's dynamite in the autopsy, I think he is not being well-advised.
For myself, I think Chauvin has a shot at manslaughter due to lack of murderous intent, but not at innocence. I just don't see how you get around the obvious reality that Floyd died while Chauvin stood on his neck, Floyd said he couldn't breathe, Chauvin kept on standing on him, and then Floyd died. Cause. Effect.
The best defence is his intent, which only he knows. But he's throwing that away for a defence that has no chance.