While I agree with this, I think the Founders' concern would go further. Even if both parents are born U.S. citizens, if they both choose to reside in a foreign country, especially Great Britain, and give birth to a child and raise the child in Great Britain, with the child maturing and residing in Great Britain past the age of 35, then I don't think the Founders would consider such a person fit to be President.
Benedict Arnold and his wife Peggy Shippen were both born in what became the U.S. I don't know if there was ever any formal proceeding which stripped Arnold of his citizenship. Loyalists weren't welcome after the Revolution but I'm not familiar with any process which stripped them of citizenship.
If Arnold and his wife gave birth to a child in Great Britain, would that child be a U.S. citizen? Would our Founders have considered that person eligible to be President?
But on the other hand, say Abigail Adams spent time with John in France and had John Quincy there, don't you think John Quincy would be considered a natural born citizen eligible for presidency?
Looks like the argument could go either way and could come down to evidence of the intentions of the parents. For example, the legal status of the parents and the child might depend on whether they intended to permanently reside abroad, which might favor no natural birth citizenship, or were only there as long as official business deemed necessary (like Adams) or on a temporary trip for pleasure which might favor natural birth citizenship.