Parallelize descriptor set updates

According to the suggestions from Nvidia, it is practicable to update descriptor sets in parallel, but according to the vkUpdateDescriptorSets, it seems that Vulkan encourages programmers to update descriptor sets all together at once.

So I got some questions:

  1. For a single thread, is it really hurts to update descriptor one by one, compares to update them together?
  2. For multi-threading, is it good to update two descriptor sets separately into two threads, compares to use one thread to update them together at once?