This eyecup is very old (early 70s), newer one is called EH-7 by Minolta.
(note: even the EH-7 was out of production long ago)
Yes this covers Sony's eye sensor so that you cannot display anything on
the rear screen, which saves battery life for me? If you want the screen
display you can cut a sensor opening to this eye-cup. Anyway any Minolta
made eyecups, magnifier, and angle finders can be used on Sony a7(R/S).

Sony should make the screen and finder as Ricoh GXR's choosable option.