Using *ELEMENT_SHELL_COMPOSITE, the through-thickness integration points are located at the center of each of layer.  *ELEMENT_SHELL uses Gaussian integration by default.  Integration point locations for Gaussian integration are tabulated under *SECTION_SHELL in the User's Manual.  I would expect Gaussian integration to be more accurate.  If you increase the number of layers in *ELEMENT_SHELL_COMPOSITE, I would expect the solution to improve.
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