The point is that you've fallen for some idiots on X making up culture war bullshit.
Kit's supposed pronouns aren't mentioned by Mozilla anywhere in any Mozilla announcements.
One news site attributes this quote to Mozilla
Kit (he/she/they/them/it) is the user’s constant companion. Wherever they choose to roam, Kit will accompany and guide them with clever, playful encouragement and support — giving the user the confidence to run free.
That's the one and only place that even remotely mentions it as far as I can tell. And it's not even a statement that it's NB or they/them... More like it's a fictional mascot call it what you want.