Actually Marco did get cut in half because he was fighting them both ( in their base forms )
He can still pose and shit because he is abusing his regeneration, and that's why all the comments are there to inform us of that, and that he can't do it for much longer.
He has the strongest DF in the manga for stalling. but fighting King and Queen at the same time, while they were in base, was pushing him to the bottom of that recovery barrel.