> > Because the result of std::bit_cast has unspecified padding bits, so x =
>
> Unless we change std::bit_cast, which is what I am proposing.


It would be an ABI break if you changed that, and compilers would
essentially have to invent new ABI for all kinds of platforms to make this
work, so the std::bit_cast that you're proposing is practically
unimplementable.