Anyone who has rafted up river knows that you can pole your way up because the drag of shallow water slows the flow next to shore. As for the current being less strong on the Ohio, that's also not true. I have navigated from Louisville to Cairo, and the flow is quite swift...depending on the time of the year.
The best time to pole up the Ohio is in the Fall...late September through mid November. Also, poling upstream is tricky because the man on port has to have a longer pole than starboard. Anyway, there are times and strategies for poling up a river, by season and studying eddies.