Hard to explain: Photoshop 20.0.1. Activate the clone stamp and the clone source panel. If you like to have a preview of the rotation of the stamp highlight the "0" in the text-area for rotation in the panel. Then bring your stamp to the area you want to work and change the rotation-value with the arrow keys. Then you will see the preview of the stamp is wrong. The right preview would be to rotate the center of the alt-click-area, but the preview in 2020 takes it from where your stamp is. So you have no preview of the actual rotation and it is not possible anymore to work with this "old" feature.