Add-ons with sound definitions under the “music” category break all music

Add-ons with sound definitions under the “music” category will break ALL music. Breaks all forms of vanilla and that add-on’s music, including the vanilla music.game. In other words, add-ons with music breaks all the music. I tested this with an add-on that directly over-rode music.game in the definitions, and then with another add-on with a simple sound defined under the music category. Both produced similar symptoms.
Further testing proves this is ENTIRELY due to the subpacks section in the manifest.json. So this report is just a repeat of MCPE-239719, just with a little bit more insight.