seems silly

Wow, the author is serious, it does not seem to be a joke! I've checked their last commit on github[0] and it has those lines:

    if (hasValidRate) {
      audio.playbackRate = playbackRate;
    }
    if (!hasValidRate && lastAudio === urlOrDataURI) {
      audio.playbackRate = 0.6;
    }

If I was code-reviewing this code, I'd recommend using else-if here, for easier understanding and to avoid accidental mistakes.

[0] https://github.com/RickCarlino/KoalaCards/commit/0750a329237...