How do we know that Sheev was lying about being able to save Padme? He never got the chance because Obi Wan kidnapped her. He was able to save Anakin after he was cut in half and fell into lave, I don't see how he wouldn't be able to fix a broken heart (probably only counseling needed for that) or a slightly harder than average child birth.
Because he told Anakin that he didn't know how to save people yet in his office