Adjusting settlement defences

I want no boiling oil/scorched sand on the gate defences.

I went to export_descr_buildings.txt and changed the "gate_defences" to 0 for all stone levels (2-4):

E.G.

stone_wall requires factions { ct_carthage, eastern, parthia, egyptian, greek, roman, }
{
capability
{
wall_level 2
tower_level 1
gate_defences 0
gate_strength 1
}
construction 3
cost 1600
settlement_min city
upgrades
{
large_stone_wall
}
}

Did it make the slightst difference? No, still boiling oil! Any answers? And yes, I did try not including the line altogether (and same result).

I have never heard of anyone successfully changing any of the attack properties for walls (arrow attack damage, range, boiling oil, etc.)