Proposed resolution:

This wording is relative to the FDIS.

1. Modify the synopsis in [unique.ptr.runtime]:

   namespace std {
     template <class T, class D> class unique_ptr<T[], D> {
     public:
       typedef see below pointer;
       typedef T element_type;
       typedef D deleter_type;
   
       // 20.7.1.3.1, constructors
       constexpr unique_ptr() noexcept;
       […]
       constexpr unique_ptr(nullptr_t) noexcept : unique_ptr() { }
   	
       […]
     };
   }
   

[ Bloomington, 2011 ]

Closed as NAD Editorial.

The synopsis in [unique.ptr.single] specifies:

constexpr unique_ptr(nullptr_t) noexcept

which looks correct to me. However the corresponding constructor in [unique.ptr.runtime] is missing noexcept:

constexpr unique_ptr(nullptr_t) : unique_ptr() { }