This is not entirely true.
One of the things about hearing is it is all about memory, IMO. If you remember a dogs sound from back when you could hear well and you lose your hearing, then get a CI. What will slowly happen is your brain will learn these new sounds from the CI and it will become what you remembered back when you could hear well.
This has happened to me with most sounds. I find sounds from the CI’s to be normal. The only time it is not is when it is a new sound that I need to learn or remember.
Music has been more challenging but very satisfying. I now can understand the words of songs that I never could before. Some music is better than others for CI.