First, the tinnitus in my damaged R-ear persists since the work related injury in May 2019 and has not diminished with OSIA2, noir would it have with any bone conduction device. I can’t speak to the traditional Cochlear implants you hear about; but I doubt it? I believe tinnitus is more of a neuro condition in the brain.
As for how they determined the inner/outer hairs of my cochlea hairs were damaged I can only assume it’s based on the Audiogram tests they ran. In particular, I would say it had to do with the progressive decline of my word/speech recognition (76% from time of injury down to 42% this past June)? I’m sure they have other means of determining this.
Keep in mind that my Phonak hearing aid did not improve matters as hearing aids in general only help amplifying sounds and if the clarity in my injured ear never improved, all I was hearing was an amplified sound of unrecognizable words or speech. That would be a great question for your Audiologist or Neuro otologist. I can only state that with my OSIA2 bone conduction implant that the clarity in which I hear things is much better. Good luck to you