The phrasing of the confederate declaration of war is entirely consistent with other US declarations of war, particularly of the 19th Century, documents that no rational person disputes are, indeed, declarations of war. And it was recognized as such by the confederates.
Understand this:
Confederate States of America - Proclamation of April 17, 1861
BY THE PRESIDENT OF THE CONFEDERATE STATES.
A PROCLAMATION. Whereas, Abraham Lincoln, the President of the United States has, by proclamation, announced the intention of invading this Confederacy with an armed force for the purpose of capturing its fortresses, and thereby subverting its independence and subjecting the free people thereof to the dominion of a foreign power; and, whereas, it has thus become the duty of this government to repel the threatened invasion, and to defend the rights and liberties of the people by all the means which the laws of nations and the usages of civilized warfare place at its disposal;
Now, therefore, I, Jefferson Davis, President of the Confederate States of America, do issue this my proclamation, inviting all those who may desire, by service in private armed vessels on the high seas, to aid this government in resisting so wanton and wicked an aggression, to make application for commissions or letters of marque and reprisal to be issued under the seal of these Confederate States.
Clear?
The difference is a vote by the legislative body empowered to declare war, and its announcement. NO such thing in your references.