Yes, the lossless audio file you're using is probably compressed — that's completely fine for this reason.
To stop YouTube auto-dub and hear the original audio, manually switch the Audio track to the original language via the settings gear on each video or Shorts. On ...
We’ve been hearing a lot about lossless audio lately. Apple Music says it has it. So does Amazon Music. Tidal and Qobuz have it too, but Spotify doesn’t. (Yet. Or still.) Is lossless audio a big deal?