As mentioned by WobblyElvis, when the oil pressure sensor is located after the oil filter then the oil filter has no effect on the oil pressure if the PD pump is still putting the same volume of oil through the oiling system.Actually, the oil pressure is driven by the high-shear viscosity, not the low-shear kinematic viscosity (KV) reported on the data sheet. The base-oil viscosity is a better approximation to the high-shear viscosity than the KV. Since you have a synthetic blend versus a full synthetic, the base-oil viscosity index (VI) will be something like 110 vs. 125 or 115 vs. 130, respectively, and you will see even more than a 20% difference in the cold oil viscosity and oil pressure, explaining the cold-oil pressure drop by switching to a better oil, and yes, there is also the less restrictive fresh and larger-capacity oil filter, further reducing the overall, across-the-full-lubrication-circuit oil pressure.
The only time an oil filter would effect the oil pressure in that situation is if the filter was so clogged up that it made the PD oil pump go into pressure relief, which I highly doubt is happening at an idle.
The only two things that effect the oil pressure at the pressure sensor located after the filter are: 1) oil viscosity and 2) oil flow volume.