Wave Of The Future “goof”

Goof listed on IMDb:

At the end of this episode, a character (unnamed, but clearly Colonel Sanders) asks Harriet if she wants her restaurant to become part of a fried chicken franchise. This would have been rather difficult in real life as Sanders was not born until 1890 and didn't start the first KFC franchise until 1952.

How is this a goof? It’s quite obviously a joke. I thought it was very entertaining!