I would not expect you to be confused about your upcoming cruise. They sent you an email with the precise dress code. They does not usually happen.
In general, when you book a SS cruise you do not get an email with the dress code. You are expected to read the website or go to some other source and figure out what is appropriate. I think it is foolish to make a dress code ship-specific. Going forward they are going to have set a single dress code for all the non expedition ships. I am confident it will be the one just announced for Nova.
I just spoke to 2 Hotel Directors who expressed frustration that corporate did not listen to them about their inability to enforce the dress code. They bot wanted it changed to what is being proposed for Nova. I think this change has been considered for a long time.