Actually, the wall between the house and the garage is not a rated wall. The IRC only requires it to be 1/2 inch sheetrock, and 5/8 inch type X for ceilings of garages where habitable spaces are above. (also, if the ceiling separates the garage from a habitable space, then the exterior supporting walls also need 1/2 inch sheetrock.)
The only rated wall required in residential construction is the wall separating individual dwelling units of two and multi-family buildings. This "party" wall must have a 2-hour rating, commonly achieved with 2 layers on each side of 5/8 inch type X sheetrock.
The IRC also makes it clear that wood or sheetrock cannot be used for the fireblocking requirement around pipes and cables. Only "approved materials" can be used.
The commentary calls the material "firestopping", the code text requires "fireblocking". I think the terms are interchangable.
