GmshReader does not implement quadrilateral boundary segments
The code for reading and inserting 'elements' contains a switch case over the element-type for actual elements and boundary segments. For the boundary segments the case element-type=3 corresponding to 4-node quadrilaterals is not implemented. As a consequence such boundary segments are not inserted and you cannot associate the boundary segment ordering in the .msh file with the insertion index and the finally the boundary segment index. Unfortunately, the reader does not print a warning or error message for this unsupported segment type.