Does nullptr_t break type punning or pointer conversions?

Consider this union:

typedef union
{
  void*      vptr;
  nullptr_t  nptr;
} pun_intended;

nullptr_t is supposedly compatible with void*. Ok so what if we initialize the void* to some non-zero value?

pun_intended foo = { .vptr = (void*)42 }; 

• This conversion is supposedly legit (impl.defined) as per C23 6.3.2.3 §4, or at least it was until nullptr_t was introduced.
• And what about union type punning? Also supposedly legit.
• And what about inspecting any type’s internal representation in C using a character type pointer, well-defined until C23, 6.3.2.3 §7.

Full example:

#include <stdio.h>
#include <inttypes.h>
#include <stddef.h>

typedef union
{
  void*      vptr;
  nullptr_t  nptr;    
} pun_intended;

int main(void)
{
  pun_intended foo = { .vptr = (void*)42 };
  printf("Value: %" PRIuPTR "n", (uintptr_t)foo.vptr);

  if(foo.nptr != (void*)42)
  {
    puts("It does not have value 42.");
    if(foo.nptr == nullptr)  
      puts("Because it's a nullptr.");
    else
      puts("But it's not a nullptr.");

    unsigned int val = *(unsigned char*)&foo; // little endian assumption here
    printf("And it has value %d.n", val);

    if(foo.vptr != nullptr)
    {
      puts("foo.vptr is however not a nullptr.");
    }
  }
}

Output on clang 16 -std=c2x:

Value: 42
It does not have value 42
Because it's a nullptr
And it has value 42.
foo.vptr is however not a nullptr

Output on gcc 13.2 -std=c2x:

Value: 42
It does not have value 42.
But it's not a nullptr.
And it has value 42.
foo.vptr is however not a nullptr.

My question: Is anything of the above (which was previously well-defined or impl.defined) now undefined/unspecied behavior? If so, where is that stated? Or are these scenarios simply not considered in C23 – a defect?