Currently, it is defined as:

template<constexpr-param T, constexpr-param... Args>
  constexpr auto operator()(this T, Args...) noexcept
    requires requires(Args...) { constant_wrapper<T::value(Args::value...)>(); }
      { return constant_wrapper<T::value(Args::value...)>{}; }

The requires clause here is
requires requires(Args...) { constant_wrapper<T::value(Args::value...)>(); }

First, the Args... here seems redundant, since we can already access the Args... in the template parameter list.
Second, the () here actually means the construction of constant_wrapper, it seems that using {} is more appropriate and consistent with the return statement and the function body.

So in my opinion, this should be better with (most likely editorial):

template<constexpr-param T, constexpr-param... Args>
  constexpr auto operator()(this T, Args...) noexcept
    requires requires { constant_wrapper<T::value(Args::value...)>{}; }
      { return constant_wrapper<T::value(Args::value...)>{}; }

Or even better with typename (probably not editorial):

template<constexpr-param T, constexpr-param... Args>
  constexpr auto operator()(this T, Args...) noexcept
    requires requires { typename constant_wrapper<T::value(Args::value...)>; }
      { return constant_wrapper<T::value(Args::value...)>{}; }

Please let me know if I'm missing anything.