>I'm not sure why they have a he-man scale going up to 11

There's a big difference between air resistance and magnetic resistance machines. Air resistance scales with the square of velocity, the same as real rowing, while magnetic resistance is linear. On an air resistance machine you can get a good workout by keeping the difficulty setting realistically low and rowing faster, but on a magnetic resistance machine you'll end up going so fast it becomes difficult to maintain good technique. The higher difficulty settings are more useful on a magnetic resistance machine.