it's an example of simpson's paradox

https://en.wikipedia.org/wiki/Simpson%27s_paradox

a worked example: if england/scotland/wales all use heart ❤️ 49% and use tears of joy 😂 at 51%, and then northern ireland was to use heart ❤️at 100%, you can imagine this would tip the whole uk over

even more freaky, you could make all 4 constituent countries use heart ❤️ at 49%, make each constituent use a different unique emoji 👍😀🥰😼 at 51% each, and then the aggregate would show that heart ❤️ is still the most used across the UK

now consider for each place on this map, they are ranking more than just 2 emojis. the map itself says that tears of joy 😂 is only scoring 5% worldwide, and that's 1st place. with margins of 5% and under to be deemed winner, it's no wonder funky effects show up