What's the difference between declval

I found that STL uses declval<T &> in implementation of std::is_destructible :

template <class>
struct __is_destructible_apply { typedef int type; };

template <typename _Tp>
struct __is_destructor_wellformed {
    template <typename _Tp1>
    static char  __test (
        typename __is_destructible_apply<decltype(_VSTD::declval<_Tp1&>().~_Tp1())>::type
    );

    template <typename _Tp1>
    static __two __test (...);

    static const bool value = sizeof(__test<_Tp>(12)) == sizeof(char);
};

It's my implementation :

template <typename T>
select_second_type_t<decltype(declval<T /* difference from STL */>().~T()), true_type>
test_destructible(int) noexcept;

template <typename> false_type test_destructible(...) noexcept;

template <typename T>
struct my_is_destructible : conditional_t<
    not is_function_v<T> and not is_unbounded_array_v<T> and not is_same_v<void, T> and is_complete_v<T>,
    conditional_t<
        is_reference_v<T>,
        true_type,
        decltype(__dsa::test_destructible<remove_extents_t<T>>(0))
    >,
    false_type
> {};

I haven't noticed any difference, why STL implements std::is_destructible as declval<T &> instead of declval<T>. I provided various T, but all returning value of std::is_destructible<T> is same as my_is_destructible