OK, after some experimentation on codepen, here's my solution. Position your element initially at 0,0. Then whatever absolute coordinates you pass to TweenLite.to( ) will be calculated relative that position. Voila! You will be animating to "absolute" positions every time.
If you don't initially position your element at 0,0 -- then whatever position you element has initially becomes it's home spot. And whenever you animate that element to 0,0 -- it returns to that home spot and not to 0,0 on your screen.
If you have element with a arbitrary starting position like that and you still need to do absolute positioning, you simply subtract the element's home position from the desired position (desiredX - homeSpotX, desiredY - homeSpotY) , and pass those values to TweenLite.to( ).
