That's true, Leitz lenses with "eyes" do not fit the Epson R-D1.
But a common misconception is that the DR Summicron does not work on the R-D1. This is false.
It works perfectly as long as the "eyes" are removed. The confusion arises because the R-D1 manual states that the DR Summicron cannot be used on the R-D1, but it's only referring to the use of the lens when the "eyes" are attached.
Otherwise, the lens is superb. The sharpness of a high resolution Summicron with a bit less contrast than the modern Summicrons, it perfectly compliments the R-D1 sensor.