Pressure Altitude in Loggers

I take as a fact that all flight loggers use a pressure transducer to
record altitude versus GPS altitude(true?). We all get a calibration
document with the recorder which spells out how accurate that
transducer is.

So why do some loggers (i.e. Cambridge 302 - a flight computer) ask
you to set the barometric pressure much as we do with an altimeter?
Others (i.e. Cambridge 302A, EW Microrecorder - both flight loggers)
do not require this. NOTE: I have flown with both a 302 and a 302A at
the same time ... and the overlapped log files in SeeYou were
identical. Therefore I the pre-flight barometer setting is not
incorporated into the FAI flight log.

I can only assume that the pre-flight barometric settings is to
enhance the accuracy of a flight computer, not a simple flight
logger. Is this increase accuracy important? Some flight software
also has the capability of setting "Altitude" (i.e. Glide Navigator
II). Why is that?

Thanks, John "67" DeRosa