After a regression in GCC 13.3, I had to add constexpr to defaulted spaceship operators in my program, and observed some discrepancies in how compilers treat some code in C++20 mode. These can be shown on equality comparison operator for the sake of code brevity below.

Example #1:

struct A {
    operator int() const;
};

struct B : A {
    constexpr bool operator==(const B &) const = default;
};

which is ok for Clang and MSVC, but GCC with -pedantic-errors option complains here:

error: call to non-‘constexpr’ function ‘A::operator int() const’ [-Winvalid-constexpr]

Example #2:

struct A {
    bool operator==(const A &) const;
};

struct B : A {
    constexpr bool operator==(const B &) const = default;
};

which ok only for MSVC, while Clang with -pedantic-errors option starts rejecting it as well with the

error: defaulted definition of equality comparison operator that is declared constexpr but invokes a non-constexpr comparison function is a C++23 extension [-Werror,-Wc++23-default-comp-relaxed-constexpr]

Are both code examples valid only in C++23 and not valid in C++20?