This is because the emoji are language specific.

Supporting phoneme-based voices in espeak-ng is currently complex,
and has issues that need to be fixed in the core code before
adding support for them.

Creating  the language  variant , swiss french. Primarily for counting
as Swiss French uses huitante  for 80 and ,  like the Belgians septante
eand nonante for  70 and 90.

1.  Store the encoding enumeration values in the Translation
    object, instead of the charset table.

2.  Use the encoding.c charset table data instead of the ones
    in translate.c.

3.  Remove the charset language file option -- it is only used
    in the Arabic language file, but is used incorrectly there.

4.  Specify ISO 8859-6 for the 8-bit encoding for Arabic instead
    of UTF-8, so that espeakCHARS_8BIT and espeakCHARS_AUTO work
    correctly for Arabic.