I have several boxes of NOS rivets and they are all of the newer style (no ribs). I would not call them "junk", just not assembly line or "concours" correct.
I can only assume that Ford changed suppliers or the oem changed their process.
As far as "trouble", that is for you to decide. Some people go the extra mile to pefect the small details such as this. I will admit, that at this time, the later model cars are not being restored to the level of detail as the early models are.