Are all characters in this series a bunch of traps!? I know that they are technically genderless they are gemstones after all, but all of them have girlish appearance and refer to themselves and each other as males (for example the usage of onii-sama instead of onee-sama in chapter 66). Pretty sure they used boku in the anime as well, don't take my word for it though because my memory ain't the best
Can't be a trap if you have no gender or genitals lol. I think they use those specific honorifics as a symbol of respect or familiarity in general though since they're all one big family in reality.
Fuck if I know, but I assume a majority or the gems use Boku, instead of Watashi, either because the gems don't have a proper concept of gender with them being rock people on a post apocalyptic planet, or the author intended for them to be more masculine despite being genderless. Watashi would be the proper pronoun to identify with, but I'm sure there's a more in depth reasoning ?.