Emojis returned by MessageReactionResponseEmoji are different from emojis attached to a reaction message

Summary

When I get a reaction event on my bot, the emoji returned is sometimes different from the emoji attached to the message. Specifically, I've noticed that when I use :santa: ( ) as a reaction in my message, my bot gets an error, as the emoji returned is converted to :Santa_Claus:, which is not a reaction my bot is programmed to respond to.

Steps to reproduce

1. Build a Python-based bot, using fluxer.py, for reaction roles.
2. Add event listeners for on_raw_reaction_add and on_raw_reaction_remove.
3. Register :santa: as a reaction role for the specified message.
4. Print the emoji returned by the event's payload.
5. Press the :santa: emoji on the tracked message.
6. The bot should (incorrectly) print out the emoji :Santa_Claus:

I'm guessing a npm-based reaction role bot would have a similar issue.