If your target response is not the flat magnitude response, the acoustical settings in the GLM setup can be adjusted as required. You can always do this manually.
The goal of a monitoring system is to faithfully convert the electrical signal presented to its inputs to sound pressure at the listening position. It should add nothing to the sound nor take anything away. GLM equalizes the response of the system to be as flat as possible thereby trying to get as close to the goal as possible.