Firstly, regarding Answers:

Uematsu didn't write the lyrics. They were handed to him before he began composing the song and also (I think) before Susan Calloway was selected as the vocalist. The English lyrics came from a person called Michael Koji Christopher-Fox, who heads up the localisation team (is that you, Ferne, or is it your boss?) after development in the lore team.

In light of this, it may be better to think of the song as being an exchange between two entities where the entity is defined by the language used rather than who is singing. Have a ponder on that and tell me what you think, perhaps in a different thread.

Back on topic...

Mjollnir, a question for you this time.
If Stahlmann/Rostnstahl is indeed the former captain Hyllfyr of the pirates of the Astalicia, how did he become disgraced in the eyes of his crew (not just the Admirality) and why is his presence still tolerated aboard the ship?
If your crew mutinies against you, you usually don't survive the ordeal and you definitely don't remain tolerated as a deckhand.
If he were just a disgraced commodore, then I would understand.