Concur. The FLW houses I've seen have all been quite consistent. I like Kentuck Knob as an example more than Fallingwater, because it doesn't have the super-obvious "cantilevered over the water" thing as a focus point, so you have to look at the whole a little more:
Consistent roofline, consistently repeated window motif, re-use of the horizontal stonework for the house, the exterior wall, and the chimneys.
The drawback of his Usonian houses is that the ceiling height is ridiculous by 2017 standards. At 6'3", I have to duck in several of the rooms, much less the doorways. Oof.
Isn't that practically one of the defining characteristics of Frank Lloyd Wright's houses?