I think it’s not pedantic because it’s very important to recognize that Lincoln in the Emancipation Proclamation was reacting to what slaves and abolitionists had decided the war was going to be about. When people say “it was about slavery” and attribute that to Lincoln, who very clearly did not believe he had the power to end slavery even despite people telling him in times of rebellion he did, and this is incredibly well documented, this takes away credit from the slaves, former slaves, and abolitionists who decided they would fight for the war to be about abolition and succeeded in that.

In another comment I shared a letter written by a freed slave to the mistress who owned his child, a letter who’s contents would have been punishable by death even from where he was writing it in the north, but it expresses perfectly the sentiment that caused the war to be about abolition. In the letter he says a thousand black soldiers and him are coming and that she will burn in hell etc.

So when we say “it’s about slavery” from the very beginning we need to be clear that it was specifically the confederates going to war over the right to own slaves at the start, while the north was going to war to preserve the Union. It became “about slavery” in the sense of freeing slaves and abolition after slaves, freed slaves, and abolitionists fought for that. It could very well have been a senseless conflict if it weren’t for abolitionists, and they fought despite the racism they faced in the north as well, because they had a higher purpose for fighting even above the generals who they fought under.