Ive experienced the same and after lots of research found two aspects. The stock tune has a soft derate at 255 F oil temps which most dont see and gde removes that, but they keep the hard derate at 269 F. The second is shutting off the egr greatly increases in cylinder temps which gde does. But in cylinder temps dont always show up as egts thats just the amount of heat being carried out the exhaust. Pilot injection is a great thing but only when used correctly.It was my understanding GDE has always eliminated pilot injection. They've gone on record as saying pilot injection is the #1 largest soot producer in this engine. I know my engine is considerably louder with the GDE tune which supports the removal of pilot injection. The regen frequency is also evidence of the lack of pilot injection with the GDE tune and proof it exists in the SKT tune.
Do you have any data to support your theory of higher oil temps with the GDE tune? Do you monitor and compare EGT's between the tunes?