Yeah it all moves once you drop off from max draw weight. Not much, but it does change since the limb timps come closer together when the poundage is relaxed.
DaveC, your suggestion to write down measurements for future comparison is good. I'm not sure with binary cams, but most other cam positions are determined by cable and string lengths. Limb tips do not move when you reduce draw weight. All you do is reduce limb pre-tension.