...pressure is variable, based on engine torque demand. The amount of pressure is controlled by the DME. There is no clutch. The pump is variable displacement with the displacement adjusted under DME control to cause the pump to produce the pressure desired. The pump defaults to full displacement and thus full oil pressure -- based on oil temperature and engine speed -- unless this is overridden by the DME.
Techs told me that at first it was a bit discerning to when driving a Porsche so equipped to when accelerating the car and using higher revs seeing the oil pressure shoot up -- like "normal" -- but to then see the oil pressure fall which is very much unlike "normal".
As for the presence of oil pressure with the engine off due to engine stop/start feature being active my info is this is provided by a small auxiliary electrically driven oil pump which supplies just enough oil to maintain a small positive oil pressure to primarily the main and rod bearings though of course the entire oil system is pressurized as the oil pressure gauge obtains its pressure reading from very far away from the oil pump from one of the cam shaft covers.
(A Porsche engine having an auxiliary oil pump is not new. My 2003 996 Turbo engine had a small engine driven oil pump specifically to supply oil to the turbos.)