Probably by Unicode 16 there will be. :p
They are very explicit that this is not permitted [1].
Also, RE :poop: 1. Huffman encoding philosophy - encode frequently used symbols using fewer bytes. 2. Standards are helpful, :poop: is very English-centric, whereas U+1F4A9 is much more interpretable.
[1] https://unicode.org/emoji/proposals.html#Selection_Factors_I...
I know, I'm just being humorously facetious. (Or at least I'd like to think that I am.)