I am not a historian, but this sounds like BS to me.
Certainly not the reason for the term Black Irish.
I need to see more proof than this article to convince me that any plantation owner would force a white woman to breed with a black man. especially after Miscegenation laws came into being.
It may be true that a few bred with blacks of their own accord and it is certain that many plantation owners bred with their black slaves, some rapes and some with consent for favors granted them.
I have never heard of Plantation owners owning Irish women and forcing them to breed with blacks.
Interesting though, but I would like to see more evidence.
Under early colonial law, slave or free status followed that of the mother, neatly eliminating any incentive for slaveowners to do any such thing.