Age 10 in 1865 (end of CW) born 1855, lived to 110(?), 1965. If the grandson heard the story at age 10, he would now be 50.
Is he that old?
If grandma only made it to 90 the grandson would now be 70!
Some memory.
He is the father in the article. I guess he could be 70. And many blacks continued working on plantation-style farms after the end of slavery, where presumably they were then entitled to some form of wage. There are still a number of “plantations” in SC and GA, for instance, that have farm or garden employees. That’s the only explanation I can think of.