You might want to look carefully at the dates on the two 1850 census pages. I have Stephen and James W. Bynum on the 1850 Marshall Co., MS with their aunt and also on the 1850 Chatham Co. NC with their father a couple weeks earlier. Time enough for two young men on horseback to travel the distance.
More reliable is the dates on the sale and purchase of land in the two areas, and any possible mention of Isaac being "of" the other area.
If the census in AL is earlier than the one in TN and the land records contain no mention of Isaac being "of" somewhere else then they probably are two separate people, perhaps related and named for and even older mutual relative Isaac.