Fruity Stereo Shaper Dephasing / Phase

I'm feeling quite lost as to what exactly this control does; I understand that it delays the signal out of phase from the opposite channel, but am confused by the percentages. Does the all-pass filter in this effect create a linear phase? Also, is 100% left or right equal to 360 degrees out of phase or does it just invert the polarity?
I saw in the manual that it varies the center frequency of the all-pass filter... Wouldn't that defeat the purpose of an all-pass?

Edit: From my understanding, phase delay is a set amount, and the % represents how far the phaser is offset at the center frequency, with this center frequency having a small 'phaser band' around it.