Well in just a cursory look at the fantastic photos... it looks to me like the main level living space which is ground level at the front of the house is a whole house level -up- from ground out the back where your patio would be.

It seems to me that they can now walk out of their main living space directly on to a beautiful deck... without walking down steps to a patio and back up steps to the main space. And I will guess also inside/outside to the kitchen, which is an obvious support to the entertaining that might happen on the deck.

Back and forth to the kitchen without up and down stairs? It looks like a fine idea to me.