I actually noticed the change in audio levels yesterday evening right before I installed 15.3. In my case, I was having to use volume levels between 60 and 70 (out of a hundred) to get a level I liked. I have a Sony Bravia 4K HDR TV. But yesterday evening I needed to adjust the levels down to between 50 and 60 to keep it from being too loud. So I think that is opposite of what you experienced. The audio was still good though, just a bit louder. After installing 15.3 this remained true. I did watch a little bit of Disney+ content with Dolby Vision and Atmos, and it was terrific on my system as usual. I also watched DV and Atmos content on some other services and all was good.