Considered - yes, implemented - not yet.
There are two feasible options. One is to only update dynamic objects (not just UE-dynamic, but also moving static meshes) and regions that were not covered on the previous frame. is somewhat problematic because it relies on the engine being able to compute accurate bounding boxes for dynamic objects, and also update parts of the static objects that happen to intersect with dynamic. Adding direct lights makes even more fun because shadows potentially depend on objects far away, and objects that receive the shadows then also need to be updated.
The second option is to freeze the voxel representation for some number of frames while the game/project knows that things are static. is relatively easy, but it will lead to stutter when something does change, and voxelization needs to happen. A more advanced version of would perform voxelization of a complex scene over multiple frames, while VXGI lighting will be either turned off or based on the previous voxel data (with the latter requiring changes to VXGI itself to handle two sets of voxel data).