None of which exist any longer, so there is no third category.
"Exactly what was the distinction between those citizens who were exempted and those who were 'natural born citizens?'"
"Few will address that when their opinion is agenda driven."
It's been addressed plenty of times. It's obvious. Americans who were alive at the time of adoption of the Constitution became citizens of the US when the US was founded. They weren't naturalized, but they weren't born US citizens either. When they were born there was no US. That's all it means. At the moment of adoption there were no "natural born citizens", but the next baby born in the US became one.
The passage is there so that George Washington and Thomas Jefferson and the other people of that generation weren't excluded from being President by the natural born clause.
Before any naturalization acts there were citizens and natural born citizens. How could that be?
Persons joined together and formed a new nation, the United States. These persons became citizens of this new nation. Their posterity became the first natural born citizens of the United States. When the Constitution was adopted citizens and natural born citizens were both eligible provided they met the other requirements of age and residency, at that time no natural born citizen could meet the age requirements. With the passage of time the original citizens died leaving only their posterity - the natural born citizens - eligible. These persons required no statute, they required no grant or dealienage