but, if the filter is less restrictive, then more oil will be pushed thru it so that the oil pressure downstream against the sensor may then be higher.
An analogy would be...on the turbo with a stock intercooler, the boost measured at the turbo may be 25 psi but the boost in the plenum may be 20.
If we change to a less restrictive ic such as a big core unit, then the boost pressure at the turbo may be 25, but the boost pressure measured in the plenum may now be 24 IF the turbo has the capacity to supply the volume required to maintain the pressure.