It can't..
You've probably did something wrong, for vanilla rome you need to change
RTW main folder/preferences/preferences.txt

For BI
RTW main folder/bi/preferences/preferences.txt

For EB for example
RTW main folder/EB/preferences/preferences.txt

In case mod I'm playing (BI modfolder)
RTW main folder/bi/eod/preferences/preferences.txt

Would there be also just an option to remove damned hills from the battle map, it would be even better..