Yes, it's true . . . . William Porterfield and his wife, Martha Alexander, did have a son named Matthew (according to information that you gave me a couple of years ago). That Matthew was b. 1743 - is that right?
The Matthew Porterfield named in James Moore's will of 1763 (when it was proved) would have been only 20 yo . . . . most likely not married and certainly not married long enough to have the four Porterfield children named in the will.
I am wondering if William Porterfield had a brother named Matthew - and perhaps he named his son after his brother??? All a mystery until someone finds some additional evidence.