These cabinets were custom built. You can get the same effect, in an prefab cabinet by purchasing end panels that are the depth you want, or larger in depth and cutting them to size.

the upper cabinet could be what we term a "deep wall cabinet" Those are typically 24" deep.

Then, have your contractor frame the back with 1x4" to allow you to pull the deep wall cabinet forward to the same depth as the front edge of the side panels. You would need to make sure you can purchase the side panels as "finished on both sides" That way you won't have a raw interal side.