I've seen several references to this happening from having too high of an oil level.
This oil system is basically a dry sump system. The oil pump pressurizes and lubes the motor, but also scavenges the oil from the crank area and pumps it back to the oil tank.
My question is if you have 2 quarts or 4 quarts of oil in the tank, how does that affect the motor? How would that make the motor spit oil into the breather through the vents?
I know in the "old days", including my Harley shovelhead, the oil pump will "bleed" oil pass the check ball and let oil gradually leak into the crankcase. When you start up the oil will get spit out the vent system. If the bike is ridden every couple weeks or so, there's not enough time to leak any large amount of oil and it just gets scavenged and pumped back to the oil tank without issue.
I'm not sure about the S&S oil system, but on Harleys there are two vents, so to speak. One is back to the oil tank and the other is from the heads. The heads have reed valve of a sort and let air up into the valve covers but not back the other way. The valve covers are then vented into the breather area and some oil, mostly vapors are then sucked into the intake and burned with the air/fuel. There are passages in the valve cover to run the oil lubbing the rockers and valves along with crankcase oily vent air through and most of it will condense and drain back down in the scavenge area to be pumped back to the oil tank.
The S&S could be a little different, but a little research should explain their venting system.
