ffmpeg combines streams?

chuck@nexus:~$ mkvmerge --identify-verbose Test.mpeg
File 'Test.mpeg': container: MPEG program stream [is_providing_timecodes:1]
Track ID 0: video (MPEG-1/2) [stream_id:e0 sub_stream_id:00 display_dimensions:1024x576]
Track ID 1: audio (AC3/EAC3) [stream_id:bd sub_stream_id:80]
chuck@nexus:~$
chuck@nexus:~$ avconv -i Test.mpeg -ss 0.000 -t 913.440 -map 0 -vcodec copy -acodec copy Test-1.mpeg
avconv version 9.16-6:9.16-0ubuntu0.14.04.1, Copyright (c) 2000-2014 the Libav developers
  built on Aug 10 2014 18:16:02 with gcc 4.8 (Ubuntu 4.8.2-19ubuntu1)
[mpeg @ 0x22cdfc0] max_analyze_duration reached
Input #0, mpeg, from 'Test.mpeg':
  Duration: 00:55:00.92, start: 0.280000, bitrate: 7255 kb/s
    Stream #0.0[0x1e0]: Video: mpeg2video (Main), yuv420p, 720x576 [PAR 64:45 DAR 16:9], 9800 kb/s, 25 fps, 25 tbr, 90k tbn, 50 tbc
    Stream #0.1[0x80]: Audio: ac3, 48000 Hz, stereo, fltp, 224 kb/s
Output #0, mpeg, to 'Test-1.mpeg':
  Metadata:
    encoder         : Lavf54.20.4
    Stream #0.0: Video: mpeg2video, yuv420p, 720x576 [PAR 64:45 DAR 16:9], q=2-31, 9800 kb/s, 90k tbn, 90k tbc
    Stream #0.1: Audio: ac3, 48000 Hz, stereo, 224 kb/s
Stream mapping:
  Stream #0:0 -> #0:0 (copy)
  Stream #0:1 -> #0:1 (copy)
Press ctrl-c to stop encoding
frame=22837 fps=2298 q=-1.0 Lsize=  805692kB time=913.40 bitrate=7226.0kbits/s
video:777399kB audio:24977kB global headers:0kB muxing overhead 0.413347%
chuck@nexus:~$
chuck@nexus:~$ mkvmerge --identify-verbose Test-1.mpeg
File 'Test-1.mpeg': container: MPEG program stream [is_providing_timecodes:1]
Track ID 0: video (MPEG-1/2) [stream_id:e0 sub_stream_id:00 display_dimensions:1024x576]
chuck@nexus:~$