Dear Alas,
Of course there was territory and parts of States that were controlled by the Yankees. But the Proclamation was about States, not territory, conquered or not.
“Actually, the Union did hold some territory in Confederate lands that this applied to.”
That is quite misleading. Your map shows a very small amount of land held by the Union. Lincoln’s proclamation had no impact on the overwhelming majority of land in the south. In 1962 that was the vast amount of land that was not affected by his proclamation.
It was a purely political move on the part of the tyrant Lincoln as was the Emancipation Proclamation which had no impact on the states that seceded. So, if slavery was so important to Lincoln why did he wait three years after the war began to issue the proclamation? I know. A political stunt!
The victors get to write history, so that is their story. By the way, the mood of the nation is not much different today — except slavery is not the issue, although its cousin, BLM is. Who really knows how this election and the aftermath will turn out? One thing is certain, the story will carry the slant of the winner.