Interesting thoughts. My take is a little different.
Yaw control to me Is very similar to other sports as far as i'm concerned. What is different is the weight distribution and height control. I lean in and "yaw" every time I turn my mountain bike. The technique is different. The balance point is different but the principle is the same. Same goes for long board skating and the feeling to is also similar to running down the line on a way. I'm not heal/tow edging as a primary turning method I'm leaning/yawing.
Your comparison to a unicycle is apt and probably closer sensation. Similar too is a wheelie on a bike. What the bike/unicycle is lacking is the height control,
To me height control is the key difference, you need to lean in whilst maintaining even balance and affecting.
I think the balance point is the single biggest issue to over come. With most other boards sports (can bikes for that matter) you can be relatively course in with your balance point it doesn't really matter if your feet are 50/50 or 60/40. It matters a huge amount on the foil. It takes time to sort that balance point and unlearn the bad habbits that you have learnt over the last X amount of year!......