The update fails and gets automatically reverted. I dont think you can get the monthly security updates without it, at least that was the case with the April rollout. Since its not immediately clear why the update fails, you can even now find quite a few people looking for help to diagnose the error online.

edit:

Here some context

https://answers.microsoft.com/en-us/windows/forum/all/kb4474...

its an easy fix for for dualboot if you can just replace grub with mbr again, but people with disc encryption are rather screwed it seems.