Oil on valve covers

While it is connected to the air cleaner the pressure in the air cleaner is atmospheric. All air cleaners were/are open to the world. When there is a pressure gradient in the intake enough for the PCV systemto work the "high side" is the breather. Your own diagram shows the direction of flow. It goes from the aircleaner, through the hose (passenger side on most Mopars), into the filter-breather, into the valve cover, through the crank case, through the opposite valve cover into the PCV, and into the carb. Negative pressure is supplied by the low pressure in the manifold. Atmospheric pressure within the air cleaner pushes it into the breather. There is circulation through the crank case as long as the PCV and breathers are on opposite valve covers and the low pressure is in the manifold because one side is at atmospheric and one side is well below atmospheric. At high rpm and/or high loads there can be too much crankcase presssure for the system to deal with. That is usually accompanied by very low levels of vacuum present in the intake and very low flow through the system. So crankcase vapor gets pushed out the filter and gets everything oily & oil can condense in the filter media and drip out.
No connection to the air cleaner housing is needed. Oil drips because 1) there's too much oil in the vapor going through it at high crankcase pressures and it's condensing in the breather filter and running out, or 2) the crankcase pressure is too high for the system to deal with.