Sapping walls

[BanditKS]

I see in the attributes for a unit there is one called "Can_Sap" i tried to attach this to a unit. no errors or crashes occurred and the attribute was added to the list attached to the unit. however it doesn't seem to allow the unit to dig under the walls.
I have two guesses as to why this didn't work. the code was removed altogether or it never worked at all in medieval 2 total war. the only time i remember digging under walls was in Rome total war. anyways just trying to see why this was added in the "export_descr_unit" but cant be used.

[axnsan]

Because there's no sap points?

[BanditKS]

Because there's no sap points?

that could be true as well which leads to the "there is no code supporting" it part i guess. anyways its no big deal i was just being curious about the code.