Very insightful post.
I wonder how many people who start the Rowing exercise in Aikido actually have rowed, or pulled a big oar, more than twelve feet to propel a water craft?
I believe that visualizing the tree types of rowing evident in the "ToriFune" undo (exercise) is beneficial to understanding the emphasis of either forward, or backward (te-sabaki) hand movements in relation to the (tai-sabaki) body movement.
However, having actual rowing experience is not at all necessary for practicing Torifune-no-gyo. Actually rowing may in fact get in the way of improving your aikido in two ways.
The first being that you may build up too much upper body strength. My experience has been that the bigger the shoulders, arms and chest of an opponent, the easier it is to drop them, and the more difficult time they have trying to lose their physical power and access kokyu power as the root of their aikido techniques.
The second way is that it is very easy to actually disturb your breathing when physically "over" training your body - hence the implementation of the "passive" FuriTama component to balance out this part of Misogi.
That being said, rowing is a great exercise, and if done correctly - i.e., with breathing - can dramatically improve one's ability to relax and find kokyu power by releasing one's physical power.
Abe Sensei said to me. "The secret of aikido, actually all budo, is to do everything with the proper breathing..." Well, that's not all he said the secret was...