Emojis are more of a unicode standard, they can be re-implemented with various themes to suit modern design trends. There's nothing wrong with redesigning your emojis to fit with the rest of your OS like you would with a system typeface.

Except there's no way for the Unicode standard to be prescriptive enough for the different implementations to express identical intent. And that's before the politics get mixed in (e.g. Apple's water gun). That's why you see many chat services and social networks shipping their own whole and opinionated emoji font: at least on their platform every user sees the same glyph and although there is still room for interpretation and misunderstanding, that's not by having too many font designers.

Just because you can, doesn’t mean you should. Approximately nobody thought Google’s current emoji family needed a total overhaul, stop breaking our pattern recognition for no reason other than your designers are bored and don’t have enough real work to do.