If there is no breather OR it doesnt breath back to the intake pipe, crankcase pressure will throw oil out of the dipstick. When I got my car, there was a hose from the intake manifold > inlet rocker cover blocked off. There was then 2 hoses going from each rocker cover to the catchcan with no breather.
The engine was throwing HEAPS of oil out of the exhaust, I reconnected the hose from intake manifold to inlet rocker cover and it stopped throwing it out the exhaust, instead it started trying to throw it out the dipstick. It was abotu then that I realised it wasn't breathing.. so yes there are wrong ways to hook them up