Update, the 4.13 preview 1 version of VXGI now supports shadowed lights. It should now be exactly the same as the 4.12.5 version, through my testing I have not seen any issues. In other news, I have opened up the issues tab for my branch, so if there are any issues with either branch, please add a new issue, make sure to prepend the issue with the branch name (4.12.5 issues will take precedence until 4.13 is finalized)
Link to Issues: https://github.com//UnrealEngine/issues