What's usually transliterated as "fu" (ふ） isn't actually equivalent to the English "fu", and to Japanese speakers, the "f" sounds like the same initial consonant as "ha", "hi", "he", and "ho". (The reason we might hear an "f" instead of an "h" is because of how Japanese "h" is pronounced in conjunction with "u".)

As to why the translation team used Huton, my guess is that they wanted to avoid confusion with "futon", since I'd say most English speakers are familiar with futons. That's just a guess, though.