The trimming advice is absolutely correct. And in a perfect and unrealistic dynamic world, common physics dictate that any attempt to steer the boat with trim alone is just as much, and likely more trouble than just putting a tiller pilot on it. Absolutely the boat will steer with trim. But all you've done is shifted your focus to fine trimming, and it's a trade off. It can be steered relatively well just by shifting your weight back and forth, (or side to side more accurately). But you are still doing something physical to steer. Tiller tamer my ass. That is simply the illusion of self steering, which basically just takes the shock loading off of the helm. Take a brand new auto, tie the wheel to the door handle, and see how far it will stay in the road. Not bloody long. And the road is static. As is the brand new steer system in the auto. The sea and the wind is dynamic, and ever changing. You can kinda see where this is going. Even the dumb videos of the amer you can see the guy release the tiller, and snatches his hand back in his lap like it was a snake, and no more than two or three seconds later has to grab it again to make an adjustment. Because the silly thing won't work more than that time typically. So if you want to go below to pee, grab a drink, work the deck, unless you are very, very quick, the boat will be heading somewhere else. Not where you want it. Because you moved. The weight changed, so off you go. Of course bigger keel boats will hold a course better, what with a helm lock, but that is an entirely different animal, I know, I've done 'em both.
Ah anyway, I fought that battle too. Break down and put a tiller pilot on it and start enjoying the boat. Without worrying that aggravating tiller. Push a button and get on with your day. There's a lotta fun to be had on the C22, but managing the helm all day ain't one of 'em...