Confirmed.

The following does not work:
$ gst-launch-0.10 -v playbin uri=http://www.cavestory.org/xm/kingstheme.xm
Setting pipeline to PAUSED ...
Pipeline is PREROLLING ...
/GstPlayBin:playbin0/GstDecodeBin:decodebin0/GstTypeFindElement:typefind.GstPad:src: caps = audio/x-mod
/GstPlayBin:playbin0/GstStreamSelector:selector_audio_src0: active-pad = NULL
/GstPlayBin:playbin0/GstQueue:preroll_audio_src0: min-threshold-time = 2850000000
** Message: don't know how to handle audio/x-mod
ERROR: from element /GstPlayBin:playbin0/GstDecodeBin:decodebin0: A Module Music Format (MOD) decoder plugin is required to play this stream, but not installed.
Additional debug info:
gstdecodebin.c(988): close_pad_link (): /GstPlayBin:playbin0/GstDecodeBin:decodebin0:
No decoder to handle media type 'audio/x-mod'
ERROR: pipeline doesn't want to preroll.
Setting pipeline to NULL ...
/GstPlayBin:playbin0/GstDecodeBin:decodebin0/GstTypeFindElement:typefind.GstPad:src: caps = NULL
FREEING pipeline ...

But downloading the file and playing it manually does:
$ gst-launch-0.10 -v playbin uri=file:///tmp/kingstheme.xm 
Setting pipeline to PAUSED ...
/GstPlayBin:playbin0/GstDecodeBin:decodebin0/GstTypeFindElement:typefind.GstPad:src: caps = audio/x-mod
/GstPlayBin:playbin0/GstStreamSelector:selector_audio_src0: active-pad = NULL
/GstPlayBin:playbin0/GstDecodeBin:decodebin0/GstModPlug:modplug0.GstPad:sink: caps = audio/x-mod
/GstPlayBin:playbin0/GstDecodeBin:decodebin0.GstGhostPad:src0: caps = audio/x-raw-int, endianness=(int)1234, signed=(boolean)true, width=(int)16, depth=(int)16, rate=(int)44100, channels=(int)2
/GstPlayBin:playbin0/GstDecodeBin:decodebin0/GstModPlug:modplug0.GstPad:src: caps = audio/x-raw-int, endianness=(int)1234, signed=(boolean)true, width=(int)16, depth=(int)16, rate=(int)44100, channels=(int)2
/GstPlayBin:playbin0/GstStreamSelector:selector_audio_src0.GstSelectorPad:sink0: caps = audio/x-raw-int, endianness=(int)1234, signed=(boolean)true, width=(int)16, depth=(int)16, rate=(int)44100, channels=(int)2
/GstPlayBin:playbin0/GstDecodeBin:decodebin0.GstGhostPad:src0: caps = audio/x-raw-int, endianness=(int)1234, signed=(boolean)true, width=(int)16, depth=(int)16, rate=(int)44100, channels=(int)2
/GstPlayBin:playbin0/GstDecodeBin:decodebin0.GstGhostPad:src0.GstProxyPad:proxypad1: caps = audio/x-raw-int, endianness=(int)1234, signed=(boolean)true, width=(int)16, depth=(int)16, rate=(int)44100, channels=(int)2
/GstPlayBin:playbin0/GstStreamSelector:selector_audio_src0.GstPad:src: caps = audio/x-raw-int, endianness=(int)1234, signed=(boolean)true, width=(int)16, depth=(int)16, rate=(int)44100, channels=(int)2
/GstPlayBin:playbin0/GstQueue:preroll_audio_src0.GstPad:sink: caps = audio/x-raw-int, endianness=(int)1234, signed=(boolean)true, width=(int)16, depth=(int)16, rate=(int)44100, channels=(int)2
/GstPlayBin:playbin0/GstQueue:preroll_audio_src0.GstPad:src: caps = audio/x-raw-int, endianness=(int)1234, signed=(boolean)true, width=(int)16, depth=(int)16, rate=(int)44100, channels=(int)2
/GstPlayBin:playbin0/GstBin:abin/GstAudioConvert:aconv.GstPad:src: caps = audio/x-raw-int, endianness=(int)1234, signed=(boolean)true, width=(int)16, depth=(int)16, rate=(int)44100, channels=(int)2
/GstPlayBin:playbin0/GstBin:abin/GstAudioConvert:aconv.GstPad:sink: caps = audio/x-raw-int, endianness=(int)1234, signed=(boolean)true, width=(int)16, depth=(int)16, rate=(int)44100, channels=(int)2
/GstPlayBin:playbin0/GstBin:abin.GstGhostPad:sink: caps = audio/x-raw-int, endianness=(int)1234, signed=(boolean)true, width=(int)16, depth=(int)16, rate=(int)44100, channels=(int)2
/GstPlayBin:playbin0/GstBin:abin.GstGhostPad:sink: caps = audio/x-raw-int, endianness=(int)1234, signed=(boolean)true, width=(int)16, depth=(int)16, rate=(int)44100, channels=(int)2
/GstPlayBin:playbin0/GstBin:abin.GstGhostPad:sink.GstProxyPad:proxypad3: caps = audio/x-raw-int, endianness=(int)1234, signed=(boolean)true, width=(int)16, depth=(int)16, rate=(int)44100, channels=(int)2
/GstPlayBin:playbin0/GstBin:abin/GstSpeexResample:aresample.GstPad:src: caps = audio/x-raw-int, endianness=(int)1234, signed=(boolean)true, width=(int)16, depth=(int)16, rate=(int)44100, channels=(int)2
/GstPlayBin:playbin0/GstBin:abin/GstSpeexResample:aresample.GstPad:sink: caps = audio/x-raw-int, endianness=(int)1234, signed=(boolean)true, width=(int)16, depth=(int)16, rate=(int)44100, channels=(int)2
/GstPlayBin:playbin0/GstBin:abin/GstVolume:volume.GstPad:src: caps = audio/x-raw-int, endianness=(int)1234, signed=(boolean)true, width=(int)16, depth=(int)16, rate=(int)44100, channels=(int)2
/GstPlayBin:playbin0/GstBin:abin/GstVolume:volume.GstPad:sink: caps = audio/x-raw-int, endianness=(int)1234, signed=(boolean)true, width=(int)16, depth=(int)16, rate=(int)44100, channels=(int)2
Pipeline is PREROLLING ...
/GstPlayBin:playbin0/GstBin:abin/GstAutoAudioSink:audiosink/GstPulseSink:audiosink-actual-sink-pulse.GstPad:sink: caps = audio/x-raw-int, endianness=(int)1234, signed=(boolean)true, width=(int)16, depth=(int)16, rate=(int)44100, channels=(int)2
/GstPlayBin:playbin0/GstBin:abin/GstAutoAudioSink:audiosink.GstGhostPad:sink: caps = audio/x-raw-int, endianness=(int)1234, signed=(boolean)true, width=(int)16, depth=(int)16, rate=(int)44100, channels=(int)2
/GstPlayBin:playbin0/GstBin:abin/GstAutoAudioSink:audiosink.GstGhostPad:sink: caps = audio/x-raw-int, endianness=(int)1234, signed=(boolean)true, width=(int)16, depth=(int)16, rate=(int)44100, channels=(int)2
/GstPlayBin:playbin0/GstBin:abin/GstAutoAudioSink:audiosink.GstGhostPad:sink.GstProxyPad:proxypad2: caps = audio/x-raw-int, endianness=(int)1234, signed=(boolean)true, width=(int)16, depth=(int)16, rate=(int)44100, channels=(int)2
Pipeline is PREROLLED ...
Setting pipeline to PLAYING ...
New clock: GstAudioSinkClock
/GstPlayBin:playbin0/GstBin:abin/GstAutoAudioSink:audiosink/GstPulseSink:audiosink-actual-sink-pulse: volume = 1.000000