I actually believe that he told them "everything" at the first hearing (like the admission that she died on board the vessel and was "buried at sea") and as we've seen up until now, the court only releases a part of it once that part no longer has influence on the ongoing investigation. For instance, I think he also admitted to dismembering the body but that part hasn't been disclosed as the police would risk people sailing up and down the coast looking for body parts, and thus risk ruining evidence. The reason why I put 'everything' in quotation earlier, is that I don't personally believe the accident-story until I see evidence that proves it.
However, it puzzles me that the prosecutor is still going for the indictment with involuntary manslaughter. I think they know something that the public doesn't - perhaps something that in fact supports the accident-story.
Now we are in full fledged crazy butcher and/or killer territory. I think that pretty much covers evasiveness and unwillingness.
And I agree, regardless of what actually happened he has turned out to be a psychopath. Dismembering a body, puncturing potential air/gas pockets then "wrapping" it in chains and finally throwing it overboard.
No, if it is an accident getting rid of the body and sinking the sub is also getting rid of evidence and would have been material in determining whether or not it really was an accident in the first place.
So either way it is destruction of evidence.