SUMMARY
Producing separate files per audio tracks will probably be used to select individual files each; to edit them separately, and so forth. The video is supposed to be empty of sound, in consequence.
However, the video contains an audio track of a mix-down of all audio tracks. It requires manual removal with e.g. ffmpeg.

STEPS TO REPRODUCE
1.  Produce a layout with one video track and two audio tracks in the time-line
2. Render with “Separate file for each audio track”

OBSERVED RESULT
You obtain a video file with all audio tracks mixed down, and two separate audio tracks

EXPECTED RESULT
You obtain a file containing the video track, and two and two files of audio tracks