people are doing this, but that doesn't mean it's legal.. If you are flying a plane that's certified for single crew ops, there is only one PIC thus only one get's to log the hours.
At the end of the day you're only fooling yourself, there's a big difference whether you arrive at your MEP/MEIR training having done 150 hours flying yourself or having done 75 hours yourself and another 75 being essentially a pax