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?

[Newsman Waterpaper]

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?

I opened the file in audcity and it does appear to be a stereo track.

[bugmenot]

So I noticed that at least one "transition" music file is a 100% mono signal (stored in a stereo ogg file)

Just listen to it, or if you don't trust your ears, use a correlation meter.

[Robby]

I can quite easily recognize a sound/music piece on mono. It just doesn't sound as right as all the other sounds that I've heard before. Slightly mind-boggling. And that feeling stuck with me partially on AAMFP too.

[madkeim]

I opened the file in audcity and it does appear to be a stereo track.

Technically it is a stereo track (I just checked in my DAW), but the stereo spectrum is so narrow that it feels mono.
I could hear a very slight tiny difference when I switched it in mono, it's almost unnoticeable.
It's pretty much the same for "music_transition_11engine_12streets".
And I agree, mono tracks are wrong most of the time, especially ambient tracks.
It is a mistake in my opinion.
I am not sure I noticed it in game though

[Romulator]

Despite being stereo or mono, the sound effects relative to the position they are created from add to the illusion of a stereo background music, which tends to overwrite the ambient music if it is present.