Wu Chia-Hsiang intended on making a straightforward period drama when he was in control, with only very few fighting sequences interspersed here and there. Hsiu Chien (James Tien) was originally going to live instead of being killed, and the conclusion probably would've been radically different and not as breathtaking.
Suffice to say, he got sacked, and Lo Wei had a completely different vision for the project. He retained the dramatics and made them even more piercing (Cheng and Chiao Mei's spirits are torn into shreds by the end of BB), but also molded the remainder of movie into a "kung fu sex horror action" film. He ramped up the gore considerably, and included copious amounts of lurid sexual content for the sake of "fleshing" out the protagonist.
Either Lo Wei was unaware of Wu Chia's original period plan, or was forced to ditch it due to the crippling production troubles.
For all intents and purposes it is two movie projects combined into one, with Bruce Lee's oozing charisma serving as the linking chain.