you shouldn't be that surprised... Huziwara is an accepted romanization in several communities... Though I do agree with you that Fujiwara is the better choice...
In actuality, Huziwara is more standardized phonemically, it's just that phonetically /h/ -> [ɸ] ~ [f] before u, and /z/ -> j before i. I'll agree with you, though, that Hepbern's 'Fujiwara" which is phonetically based makes much more sense.