Well when it goes into production for China it will be given a J-number (9 in all likelihood) As I am sure you know the J means something in Chinese. Do you know what it is?
The only aircraft that get a "F" prefix are ones that are independently funded rather than government funded. When the Fc-1 goes into service then it will drop that code and become a J number.
If others are confused that is their problem not mine, as it is fairly simple.
J is a first letter of romanized pronunciation of Chinese 歼, the first character of 歼击机 - meaning "Fighter".
Thus, I would probably guess J and F have the same meaning.