Setting a sample rate in the web audio API

Hey, you probably already know my JS GameBoy Color emulator project
https://github.com/grantgalitz/GameBoy-Online
The thing is, I'm wondering why the web audio API refuses to allow me to set
my own sample rate (I want 70khz). Right now I have to set the sample rate
to that already found in the API itself:
audioSource = audioContextHandle.createBufferSource(); //We need to create a
false input to get the chain started.
audioSource.loop = false; //Keep this alive forever (Event handler will know
when to ouput.)
settings[14] = audioContextHandle.sampleRate;
audioSource.buffer = audioContextHandle.createBuffer(1, 1,
settings[14]); //Create
a zero'd input buffer for the input to be valid.
audioNode = audioContextHandle.createJavaScriptNode(settings[18], 1,
2); //Create
2 outputs and ignore the input buffer (Just copy buffer 1 over if mono)
audioNode.onaudioprocess = audioOutputEvent; //Connect the audio processing
event to a handling function so we can manipulate output
audioSource.connect(audioNode); //Send and chain the input to the audio
manipulation.
audioNode.connect(audioContextHandle.destination); //Send and chain the
output of the audio manipulation to the system audio output.
audioSource.noteOn(0);

settings[14] being the sample rate 70000.
I need to do this to get it to work:
settings[14] = audioContextHandle.sampleRate;
Which effectively forces me to use the API's arbitrary sample rate instead
of one I want to use.