Some codes provide an offset parameter that defines the composite location in relation to the element reference plane.
See e.g.
- the Z0 parameter in the Nastran PCOMP: PCOMP
- the OFFSET parameter in Abaqus SHELL SECTION: *SHELL SECTION
This means that the reference plane of the element is not necessaryly the midplane of the composite (i.e. the dotted line in your center image could be moved up or down).