That is only because of relatively recent misinterpretation of the 14th Amendment (which was passed only to make former USA slaves citizen so that they would not be stateless). The 14th Amendment does not mention and has nothing to do with the definition of natural born Citizen.
If Harris had been born before the 14th Amendment she would not have been a citizen at all. Obviously the 14th Amendment was not part of the Constitution when the Founders made natural born Citizen a presidential job requirement, so if in the Founders' time someone with birth circumstances exactly Harris would not have even been a citizen, then the Founders could not have possibly considered someone like Harris to be a natural born Citizen. Q.E.D.
Say what? Do you have any inkling of the history of immigration in this country?
For the first 100 years post-ratification what percentage of children do you expect were born of parents of foreign birth?
By your logic they couldn't be citizens and couldn't bear citizens.