The legal process of incorporation of Hesse-Kassel into Westphalia would have addressed its debts unless the debt had been otherwise been legally assumed by another entity. There might have existed term in the original deed, such as the collateral or designated income, which caused the instruments to have "survived" the incorporation.

As in my other post, I agree with your "to whom" question.

Whatever else, independent of decisions being "wise" or "correct" or "legal", there are few actions by Napoleon which were "pointless" as to his intentions. - R