qɥb
I suspect if CFGS is 1 then EEPGD is don't care.

That is my suspicion as well.  The datasheet should make that clear, like:
 
bit 7       EEPGD: Flash Program/Data EEPROM Memory Select bit
              If CFGS = 1:
              This is a "don't care" bit.
 
              If CFGS = 0:
                    1 = Accesses program space Flash memory
                    0 = Accesses data EEPROM memory