C++20 constrained auto&& not a "universal reference"

See more:

C++20

"auto&&" preceded by concept "con" is not a "universal reference as shown below. Remove the constraint by changing "con auto&&" to "auto&&" and it is a "universal reference" (no compilation error). Could someone please explain why?

#include<concepts>
class Base { public: Base() {} };
class Derived : public Base { public: Derived() {} };
template<typename t>
concept con = std::is_class_v<t> && std::derived_from<t, base>;

void f(con auto&& x) {}

int main()
{
	f(Derived()); // r-value: Ok
	Derived d;
	f(d); // l-value: MSVC ERROR "no matching overloaded function found"
}

What I have tried:

Internet search for the specific case described here.