I received a note back from the Census Bureau, Geographic Products Management Branch, regarding the data error I discovered. Turns out the Tiger/Line product is not at fault as I suspected. The fault, dear Brutus lies in ourselves, not the stars... Somehow, during the automated process of loading the Tiger/Line data, the "I" records for Jefferson County, KY didn't get loaded. I will have to write a program to verify the entire data set now.
Actually, this is both good news and bad. Good news in that the Tiger/Line data has been vindicated. Bad news in that there was a glitch in the automated process to load the data. Regardless, writing a verification program will give me greater confidence in the data.