When I generate them, their tabs do show up and the image files are created on disk, but when clicking on the tab for either of those 2 statistics, they aren't shown in the report.

Turns out the report link/anchor id's don't match:

singleStatistic_gifts_slice1_PICKED_MOVE_TYPE_BEST_SCORE_DIFF
subSingleStatistic_gifts_slice1_PICKED_MOVE_TYPE_BEST_SCORE_DIFF