The "map" option is working correctly. Remember, when you specify one of these options, whether it is "pixels", "dbu", or "map", the dialog needs to be designed around that option.
When the "dbu" option was added long ago, it worked correctly for the majority of people, however the method it used was a generic dialog sizing method. The "map" option is an updated method that uses the now recommended method for mapping dialog sizes across different versions of Windows with different system fonts and DPIs.
Once you design a dialog around one of these options, its size and contents should remap correctly across different Windows versions that use different system fonts and DPIs.