It's nothing but a worm drive pump. The shaft that goes throught to the gear is sealed. You can fill that case with water and it will do nothing but weigh a little more. Once the pump is removed it's just a little nub turning in there.
Why do you believe they need a block off?
True question, not flaming. I don't see any diff. between a block off plate and leaving the drive mech. in. Hell you can even take the gear off if you want.
I don't get it????
A