One thought I just had about that research is that it’s looking at the changes in meaning of emoji in usage on Twitter from 2012 to 2018. What that misses is that the people who either don’t understand the meaning of an emoji or disagree with that meaning aren’t going to use it at all. I almost never use emoji, and when I do, only a very small number of them in uncontroversial ways, because I can’t say that I even know how they might be interpreted.
If you think back to the discussion we had about which emoji to provide here in Discourse, it became very clear that people really didn’t agree about quite a few of the possibilities.