tbqh its probably less a vindictive NA localization team and more following NA laws / guidelines. Im not entirely up to date but I have to imagine the NA ratings boards wouldnt allow even 'digital' underage / teen nudity without either heavy fines or getting some pornographic rating slapped on the game.
To that end, the word 'slave' within context to just the 'name' of a weapon probably doesnt even ping on the NA rating board. Because context is key as far as these things go.
Until you actually change american laws / regulations; you will likely always see this sort of change within the gaming industry specifically.
That being said; its also horrifically heteronormative in how the ratings are done too. Notice how we have 90000 different skimpy-nipple-paste-and-thong outfits for female models etc (because that is their main target demographic / what sells). Justifying that on a child-like model (or one that is canonically supposed to be "underage") is likely what they are trying to avoid