Vorbis borks a pure 440Hz sine wave at the highest quality level

A test case:

oggenc -q10 *wav
WARNING: quality setting too high, setting to maximum quality.
Opening with wav module: WAV file reader
Encoding "01_440hz Tone.wav" to
         "01_440hz Tone.ogg"
at quality 10.00
        [ 99.9%] [ 0m00s remaining] /

Done encoding file "01_440hz Tone.ogg"

        File length:  14m 42.0s
        Elapsed time: 0m 09.2s
        Rate:         95.4935
        Average bitrate: 26.0 kb/s

Components versions:

$ rpm -qa | grep vorbis
libvorbis-1.3.4-2.el6.i686
libvorbis-devel-1.3.4-2.el6.i686
vorbis-tools-1.4.0-16.el6.i686