Falling building deals huge TRUE damage to caharacters head hitpoint only.
According to (Bad usage example on wiki for Damage System)[https://community.bistudio.com/wiki/Arma_Reforger:Damage_System] it isn't the best way to destroy a entity, because of possible "Terminator mod" (or mod that allows survival in falling building).
So it will be better to use better damage type (COLLISION or KINETIC for example) and deal it to all hitpoints.