Notice the difference here?

With the K4/JGDR class you have the "or similar" verbiage, whereas with the X4/XFAR, it's "Exact Model". While you have a right to be annoyed, based on the way they position these vehicle classes, they have the right to sub-in/out makes/models as they choose. The makes/models are examples of what you could get not necessarily what you would get if you had a reservation for that class unless it explicitly said, "Reserve this Exact Model". That may not be what you want to hear, but that's the way it works with Hertz.