What could be the cause of a cookie bite loss?

I have had a cookie bite loss in both ears either since birth or since around 5 years old, i have audiograms dating back to nursery age, lucky for me the audiogram has stayed the same for the last 20 years or so.

There are no other members in my family with any hearing loss so surely this cannot be due to genetics?
One audiologist told me that it will be most likely due to complications at birth, so the hair cells in my ears got damaged at birth and then i ended up with this particular hearing loss.

Anyone else have a similar hearing loss and know how they got it?