Mono music files - why?

[bugmenot]

Okay, this is just out of pure personal interest and maybe some of the "sound guys" are reading this forum and can answer this.
AAMFP is of course a game that should be played with headphones, and something that you can hear very clearly when wearing headphones is when some sound source is completely mono. It's just instantly obvious because things feel crowded at the center and the rest of the audio spectrum feels empty.
So I noticed that at least one "transition" music file is a 100% mono signal (stored in a stereo ogg file), namely "music_transition_12streets_13pigline.ogg" (which seems to be a duplicate of "Factory_tension_loop_160.ogg"). It's an interesting track, but I'm sure it would sound even better in stereo.
While analyzing the file in an audio editor, I also instantly noticed the steep lowpass filter at ~18KHz, which suggests that this was originally an MP3 file, converted to OGG. Am I right in my assumption that possibly a draft file slipped into the game here, and it is a mistake that it's entirely mono?