that is DontNeedFederateDefinition vs. MustBeFederateDefinition.
Formal not-federate-definition way need restriction for creating emoji. Emoji appearance must be definitely derived from char sequence.
ZWJ-joined Emoji sequence is matched for that needs.
Fun way need federation of emoji definition. because Fun emoji sometime meaningless or can't derived from char sequence.
but It means implement Fun way is really hard and RemoteEmojiUpdateWorker will appear😱 .