type argument of selectors and summon command not working with entity id aliases

The bug

Entity aliases such as "Cat", "WitherSkeleton",... are not working with the /summon command and the type argument of entity selectors. They are however used by the spawn eggs. Inspecting the NBT data of the WitherSkeleton spawn egg shows:

EntityTag:{id:"WitherSkeleton"}

How to reproduce

Use the following command

/summon WitherSkeleton