The gun emoji is used to make death threats etcetera. Why do you want that on a social media platform? It's not politics, it's just decency.
In fact, I can't recall a single time I've seen it used in the context of water guns.
People posting "<Skull><Water_Droplets><Water_Gun>" on Twitter/TikTok/whatever are just doing the emoji equivalent of saying "I'm gonna shoot this guy, in Minecraft."
Is it really better that the emoji is technically not an actual pistol? Is that gonna be the thing that stops people from making threats online?