It looks like saw, rev and square of the LFO have no influence on amplitude modulation. The triangle and random waveforms do work.
That seems really weird. Especially since square would be a much more useful modulation for amplitude then random IMO.
When you modulate filters or amps with LFOs or Envelopes, you have to imagine the filter or amp having a MAXIMUM value. If you start the modulation near that maximum value and move upward, you won't get much change.
Another example is adjusting Cutoff and Envelope amount. Depending on the Cutoff level and initial Envelope amount, you may not hear any change at all. You will have bring the Env amount down a bit and adjust the Cutoff before you can hear what the Env is doing.
However, when you modulate pitch with LFO or envelope you have a much wider range and you wont find yourself hearing no change like the example above.
All Analog synths do this to some degree, digital synths compensate with software since the sound is 100% software anyway.