True, but that won’t stop the courts from declaring a law nullifying citizenship from persons who were mistakenly granted it under the current misinterpretation as being ex post facto and therefore void.
I haven't heard anything making it retroactive. The simplest thing for Trump to do is change the policy going forward to disallow birthright citizenship by birth tourism and by illegal aliens. That alone would make a lot of people happy and all he would be doing is reversing an executive policy, not a law and not any interpretation of the 14th Amendment.
"All persons born or naturalized in the United States and subject to the jurisdiction thereof,..." Children born to illegals or tourists do not qualify as subjects of American law. Therefore they do not get citizenship.