It does. WAV は非圧縮 PCM: ビット精度と編集可能、ステレオ分あたり約 10 MB. That decides whether a gain change is an exact edit of the samples or has to go through a re-encode.
透明度の決定は，透明度の変更を行う段階である。 That is the step most people actually came for, and doing it after WAV のボリュームを調整 rather than before it means the conversion works from the file you finally settled on.
