No spin, the Confederacy was loosing the war. Davis knew that, his offer of negotiate emancipation for European diplomatic recognition was simply a last ditch desperate effort to try and save a cause that was already lost. Never mind that it would have taken an amendment to the Confederate Constitution to accomplish that emancipation.
You say last ditch and desperate blah blah blah. They were still very much in the war. Obviously neither Davis nor the Confederate Congress believed it would have taken a constitutional amendment to the Confederate Constitution to agree to a treaty that would have abolished slavery. Treaties have the force of constitutional law.