Back when WhatsApp first brought emoji’s into the chat app, there was no Android emoji set, the company was forced to import the ones that were used in Apple iPhones. Later, Android brought its own version but WhatsApp didn’t adopt them. The reason was that not all Android phones at the time natively supported those emojis, and also because they looked horrible.
Many years later, WhatsApp has decided to change direction. As evidenced by an upcoming update, the company has made its own emoji set with inspiration from Android Oreo, Apple’s iOS and Twitter’s emojis. The differences are subtle and that is a good thing since drastic changes would confuse people and maybe get lost in translation. The new emoji’s are still based on the Unicode for compatibility on all platforms.
It is unclear if the new set will be available across all the platform or only on non-Apple devices but time will tell. It is not uncommon for companies to shed off their dependence on others as they grow, Apple did the same with Google Maps and Microsoft did it too with Google Search after Bing came along.