Updating AS leads to extremely low traversal performance

Here’s a pictorial example of what I mean, just for fun. First the built AS with group bounds, and some spheres marked for replacement:

Note that there is minimal overlap, only one tiny sliver of space that needs to check 2 group bounds. So even though I only picked 4 spheres to move randomly, I end up with 100% overlap in the center of the scene, where I have to traverse all group bounds.

This is just a contrived example, but hopefully explains clearly how moving only a small subset of your primitives a long distance can severely degrade the entire structure when trying to use a BVH update.