How to detect whether a type is std::tuple or not?

Why I have strange output for this code? How to test for a type in the right way?

#include <iostream>
#include <tuple>
#include <type_traits>

template<typename T> struct is_tuple : std::false_type {};
template<typename... Ts> struct is_tuple<std::tuple<Ts...>> : std::true_type {};

struct TraitBlock {
    using BlockLocation = struct { std::uint64_t x, y, z; };
};

struct TraitRock {};

struct ItemTemplate{
    static constexpr auto traits = std::make_tuple(
        TraitBlock{},
        TraitRock{}
    );
};

int main(){
    using A = std::tuple<char, int,double,char>;
    std::cout << is_tuple<decltype(ItemTemplate::traits)>::value 
    << is_tuple<decltype(std::make_tuple(
        TraitBlock{},
        TraitRock{}
    ))>::value
    << std::endl;
}

I use mingw64-gcc 7.2.0 with -std=c++17, I got output "01" Why I got two different output? Aren't they the same type?