It's the same with grenades too on houses.
Well they specifically changed grenades type to "small explosives" so that they wouldn't do as much damage to buildings. That was one or two patches ago. It's possible they did the same thing with Satchel Charges but that doesn't make a lot of sense. It was sort of meant to counter bunkers and damage structures and now it just doesn't. I think it's probably a bug - I certainly hope so.