Based on this reddit post (believe what you will): https://www.reddit.com/r/GradSchool/comments/ft094n/comments_from_a_grfp_reviewer/, reviewers assign scores and then Z-scores are calculated for each reviewer (i.e., a lower score from a consistently hard reviewer might have a higher Z-score than a higher score from a consistently easy reviewer). These normalized Z-scores are then used to rank order applicants within a review panel and the lists are sent to NSF. The E/VG/G/F/P labels are assigned by each reviewer and are not subjected to the normalization process, so this would explain why some 3x E/E's don't get awarded and some folks with a number of VG scores do get awarded.