Why would one need higher rights to choose where to put it in the tree than the right it takes to add it in the tree?
This is fine when the parent page has a few child pages (so they are always listed). My worry is that when the parent page has a lot of child pages, users could abuse the pinned child pages feature to "promote" their pages to the top of the list visible in the tree, a list that is limited due to pagination. So by pinning a child page they don't only reorder the child pages but can also "push" a child page (that was otherwise not visible initially) to the top of the visible list.
