See here, issues I find with the description:
- The bounding box seems not to play any role in the pivot determination. This might be a blender bug or I might be misunderstanding the functionality. See the attached bbox.blend file, which contains a cube which has its origin shifted to one of the corners. The bbox of the cube is still the whole cube, but when the pivot is set to bbox center the rotation is around the corner, not the center. Perhaps it's the bounding box of object centers that is used (when multiple objects are selected), that is not completely clear to me as the text under In object mode reads "More precisely, the centers of objects are taken into account." But if that's the case then showing bounding boxes of individual objects, as in the top figure, makes no sense.
- It lists the hot key as comma, but it's period
This is with 2.81.12 (git 3e230cecf0c5) on Arch Linux.