I don't know anything about the treatment. But to be hereditary the genome changes would have to affect gametes. If genes are only changed in other targeted tissue then the changes wouldn't be inherited.

No
The gene therapy is applied locally. They operate on the ear to enable access to the relevant tissue and then apply the therapy. So it should only affect cells in the ear.
Additionally, it is unclear to me whether the therapeutic gene is integrated into the genome. It might not be.
For transmission to offspring, you would need to edit germ line cells (sex cells) and you would need to integrate the gene into the genome.