Big old myth.
Warped rotors don't cause brake pulsation. They can't because of the design of the brakes. The floating calipers will put even pressure on the rotor, and float along with the warp. Fixed calipers will transfer fluid to the other side if the rotor is warped, but either way, you are still applying the same pressure to the pads, the pads are providing the same pressure to the rotors, so the problem HAS to be an uneven coefficient of friction over the surface of the rotor.
What causes brake pulsation is deposits on the rotor. You probably can't even see them, but the extreme heat burns pad material into the cast iron rotor. It has a vastly different coefficient of friction and therefore causes brake pulsation. In extreme cases, the deposition can be great enough that it alters the thickness of the rotor. In those situtaions, you typically feel it kicking back through the pedal in addition to pulsating brake torque.
The single most important factor in not getting brake pulsation is to properly bed in your pads when they're new. Not doing this step will almost always eventually lead to trouble.
Do a search for "warped rotor myth" and you'll turn up tons of tech on it.