Ok I will take a stab at this. The ring, middle crank seal does not make a perfect seal. The ring will let a little gas, oil and air past it. This is why you can keep filling the hose and the oil just bleeds into the crankcase, because a metal ring on a metal surface does not make a tight seal. Just like a piston ring will leak air by it when you do a leak down test on a motor. Not a perfect seal. Running a line from the bottom of the case to the water pump shaft chamber worked good on the older upright twins, but not so well on the laydown twins. Why I dont know. I just know it does not work out as well on they laydown motors. As I have seen problems when this has been done on the laydown motors. Maybe they enough more efficient that you dont get the transfer like on the uprights.
On the old thundercats there was no ports for lubricating the counterbalance shaft. Cat figured there was enough oil and gas that got by the ring (crank seal) to properly lube the counterbalance shaft. It did supply some lube but not enough as a lot of us found out and had to install a grease fitting in the case to oil the counterbalance shaft bearings.
I will have a sled at my shop on Tuesday that has the cover drilled and a grease zerk installed to oil or grease (which ever you prefer) the water pump shaft. The housing behind the cover also needs to be drilled. If I get time I will pull it apart and take some pictures for you guys. This motor in this sled has never had an oil injection system on it, just the zerk and a block off plate. Sled has never had any cranks issues with over 4500 miles on it.
Just my .02