Some people pick up towing fairly quickly, most get it eventually, but some never do.
It doesn’t take too much for the average mariner to learn to tow offshore point to point. It takes a lot of hands on practice to become a good barge handler.
I hear that the other TOAR courses have very high pass rates. I suspect that they all claim to be selective and rigorous. If Seattle does not have a very high pass rate, it won’t survive. Word will get out quickly and no one will risk $2000 if it’s not pretty close to a sure thing. There are other places to go for a one day TOAR.