[aecay]

AFAIK vanilla GNU emacs uses NeXTStep APIs, which are also implemented by the GNUStep project[1]. So if/when X11 (and the many libraries that sit on top of it) learns how to do color emoji, then GNUStep can implement the Mac OS API, and emacs will support it.

The GNU position wrt. Mac support is that only the APIs that GNUStep also supports can be used. You may disagree with the principles underlying that choice, but it is a long-standing policy of the project. It was a mistake (according to this policy) for them to merge the emoji support, and when the mistake was pointed out they removed it. So it's a bit more nuanced than your comment makes out.

[1] http://www.gnustep.org/