I definitely think Juneteenth fits best as the final application of that proclamation. Although it’s slightly incongruous with July 4th celebrating the Declaration of Independence (rather than the end of the war), I think what distinguishes them is who declared the independence: the oppressed or the oppressor.
Independence Day celebrates the oppressed declaring their freedom and then later fighting to win it. An EP day would celebrate the oppressor declaring the freedom of the oppressed, so it seems less like it’d be celebrating black freedom and more like “wow guys look at what a good thing we did”. I’d imagine the EP falling on January 1st does its viability as a holiday no favors either.
The original Wired article is a substantially better source than the IBT, which is slop that owns the likes of Newsweek and the Latin Times. On Wikipedia, we avoid citing it wherever possible.