That is exactly right. The Emancipation Proclamation did not free slaves in Union states.
While it does reflect Lincoln’s humanity and hatred of slavery it was a military expediency intended to hurt the South’s war-making ability and it did.
History is a story of unintended consequences and plans being changed because of developments.
An independent observer at the London Spectator said much the same as you about Lincolns Emancipation Proclamation:
The Government liberates the enemys slaves as it would the enemys cattle, simply to weaken them in the coming conflict . . . the principle asserted is not that a human being cannot justly own another, but that he cannot own him unless he is loyal to the United States.