Why does std::is_rvalue_reference not do what it is advertised to do?

For example if I have

#include <type_traits>

struct OwnershipReceiver
{
  template <typename T,
            class = typename std::enable_if
            <
                !std::is_lvalue_reference<T>::value
            >::type
           >
  void receive_ownership(T&& t)
  {
     // taking file descriptor of t, and clear t
  }
};

copied from How to make template rvalue reference parameter ONLY bind to rvalue reference?

the poster uses !std::is_lvalue_reference instead of the immediately more obvious std::is_rvalue_reference. I've verified this in my own code where the former works and the later doesn't.

Can anybody explain why the obvious doesn't work?