You only pull up to the PLIs (stick shaker) if ground contact is still imminent after the initial pull up to 20 degrees. The only time you wouldn't achieve 20 degrees is at very low speed - if you've got a low speed event and GPWS then you really have screwed up. A pull up manoeuver from a baulked landing could result in a tail scrape, then massive energy and ROC which would likely bust the MAP altitude. It's not necessary and would be innapropriate.