Why dioes TChannel appear to have no code?

From AUDIO.BMX:

Type TChannel
	Rem
	bbdoc: Stop audio channel playback
	about:
	Shuts down the audio channel. Further commands on this audio channel will have no effect.
	End Rem
	Method Stop()
	End Method
	Rem
	bbdoc: Pause or unpause audio channel playback
	about:
	If @paused is True, the audio channel is paused. Otherwise, the audio channel is unpaused.
	End Rem
	Method SetPaused( paused )
	End Method
	Rem
	bbdoc: Set audio channel volume
	about:
	@volume should be in the range 0 (silence) to 1 (full volume).
	End Rem
	Method SetVolume( volume# )
	End Method
	Rem
	bbdoc: Set audio channel stereo pan
	about:
	@pan should be in the range -1 (full left) to 1 (full right).
	End Rem
	Method SetPan( pan# ) 
	End Method
	Rem
	bbdoc: Set audio channel depth
	about: 
	@depth should be in the range -1 (back) to 1 (front).
	End Rem
	Method SetDepth( depth# )
	End Method
	Rem
	bbdoc: Set audio channel playback rate
	about:
	@rate is a multiplier used to modify the audio channel's frequency.
	For example, a rate of .5 will cause the audio channel
	to play at half speed (ie: an octave down) while a rate of 2 will
	cause the audio channel to play at double speed (ie: an octave up).
	End Rem
	Method SetRate( rate# )
	End Method
	Rem
	bbdoc: Determine whether audio channel is playing
	returns: True if @channel is currently playing
	about:
	#Playing will return False if the audio channel is either paused, or has been stopped
	using #Stop.
	End Rem
	Method Playing()
	End Method

End Type

This doesn't appear to be a case of the methods for the type not being implemented but the regular commands being implemented, because the regular commands seemingly call these empty methods:

Rem
bbdoc: Stop an audio channel
about:
Shuts down an audio channel. Further commands using this channel will have no effect.
end rem
Function StopChannel( channel:TChannel )
	channel.Stop
End Function

Rem
bbdoc: Determine whether an audio channel is playing
returns: #True if @channel is currently playing
about:
#ChannelPlaying will return #False if either the channel has been paused using #PauseChannel,
or stopped using #StopChannel.
end rem
Function ChannelPlaying( channel:TChannel )
	Return channel.Playing()
End Function

What gives?