Sumatra is also possible, that's true. I saw older Batak architecture at the Toba lake, they are very similar to the Toraja houses.
Medan, Bandar Pasir Mandoge, Habinsaran
Not my pics, but I have been in both actual places (they are more of a museum nowadays than inhabited). The latter pic is near the King's graves of Ambarita on Samosir Island. Close to the first pic I visited a funeral ceremony once. That was very impressive.
I found some pics of the Rantepao area I took