Ah if anything its the volume that's different. On SteamOS there are 2 speaker devices in the audio settings and one isn't affected by the volume buttons and acts as a sort of multiplier for the speaker volume. For whatever reason on SteamOS this slider was set to 30% for me. At some point when I learned of this I turned it up somewhat, maybe to 60%, then I just kind of lived with that for several months. On Bazzite this same slider exists but it's at 100%.