Hi Dave,
The Osia isn't a cochlear implant--it's a bone-anchored conduction device. It can get confusing because the brand/manufacturer of the Osia is named Cochlear and the Osia is an implant--but it isn't a cochlear implant.
Cochlear implants (and this is my low-tech understanding) get wired right into the auditory nerve and, as you said, many people have to kind of retrain their brains to learn to interpret what they're "hearing" as the sounds they're used to hearing. Conversely, bone-anchored conduction devices are attached/anchored onto the skull, behind the ear. They have external pieces that pick up sound via an external microphone, and the sound is transmitted electronically to a vibrating piece that rest on the skull. The piece vibrates and your ear receives those vibrations just like it receives regular sound. The Osia's external piece connects to the internal component via magnet. There are no wires and it doesn't access your auditory nerve, like cochlear implants do. The sound is just like the regular sound you're used to hearing so there's no need to retrain your brain and you can enjoy music as much as you ever did with traditional hearing. It's truly amazing. I like not having hearing aids in my ear and I love that what I hear is just like natural sound. The magnet is comfortable to the point of forgetting that you're wearing the device.
Let me know if you have any additional questions!