DVD "fake" 5.1 DTS is actually stereo... how to fix empty channels?

[Sapito]

So, I have these DVDs from a boxset that all have a 2.0 DTS track. Except one that shows up as 5.1. When inspecting the VOB file it looks like a proper stereo track, but MakeMKV, eac3to, mkvtoolnix, all produce a "fake" 5.1 track with a strange tag when seen with MediaInfo ("Channel(s)_Original") that suggests it's actually stereo. When opening said track with Audacity the first two channels have sound, the rest are empty. See the mediainfos below:

Original VOB from DVD

Audio #2
ID                                       : 189 (0xBD)-137 (0x89)
Format                                   : DTS
Format/Info                              : Digital Theater Systems
Muxing mode                              : DVD-Video
Duration                                 : 17 min 16 s
Bit rate mode                            : Constant
Bit rate                                 : 755 kb/s
Channel(s)                               : 2 channels
Channel layout                           : L R
Sampling rate                            : 48.0 kHz
Frame rate                               : 93.750 FPS (512 SPF)
Bit depth                                : 16 bits
Compression mode                         : Lossy
Stream size                              : 93.2 MiB (9%)

DTS extracted from the MakeMKV remux

Audio #2
ID                                       : 3
ID in the original source medium         : 189 (0xBD)137 (0x89)
Format                                   : DTS
Format/Info                              : Digital Theater Systems
Codec ID                                 : A_DTS
Duration                                 : 1 h 12 min
Bit rate mode                            : Constant
Bit rate                                 : 755 kb/s
Channel(s)                               : 6 channels
Channel(s)_Original                      : 2 channels
Channel layout                           : L R
Sampling rate                            : 48.0 kHz
Frame rate                               : 93.750 FPS (512 SPF)
Bit depth                                : 16 bits
Compression mode                         : Lossy
Stream size                              : 391 MiB (9%)
Title                                    : Surround 5.1
Language                                 : Japanese
Default                                  : No
Forced                                   : No
Original source medium                   : DVD-Video

It's impossible to use "-downStereo" with eac3to, I get this:

a03 Extracting audio track number 3...
a03 Decoding with libDcaDec DTS Decoder...
a03 Encoding FLAC with libFlac...
a03 libDcaDec output changed from 6 channels, 48kHz to 2 channels, 48kHz.
a03 Creating file "C:\lol.flac"...
Aborted at file position 262144.

So far I can extract the "5.1" DTS as is, open it with Audacity, delete the empty channels and export that as FLAC. Ironically the 755 kbps DTS file goes down to a 415 kbps FLAC. Lol, it's an old movie with shit sound, there must be so little data that the fixed bitrate DTS is a waste. In fact, both channels in Audacity looked the same, it must be a mono track originally.

Aside that, what can you do in these cases of "fake" DTS tracks? How can you get rid of the empty channels?

[pandy]

Old movies are stereo at best - most cases audio was considered unimportant (used to create mood or as dialogue with some "fill gap" music).
Of course you can convert DTS to 2.0 channel. Alternatively you could in theory create if not multichannel audio then at least artificially created room characteristic multichannel (see no point when you can do this in real life using AV amplifier embedded DSP).