Seems like a frill. A paddle would be handier, I think.
Well yes, it would be if it was already in your hand. But assuming you are STEAMING along in your canoe, you'll have one hand on the tiller and the other on the engine controls, so you'd have to drop everything and pick up a paddle. Seems easier to just throttle back, put it in reverse and throw the tiller over. I'd say that once you put a steam engine in your canoe, you no longer truly have a traditional canoe anymore, but rather a small steam launch, and as such it probably should be operated as such ...... or so I think.
Mind you, I've got about ten thousand miles under the keel of my canoe, in all sorts of waters, so I've certainly got nothing what-so-ever against a traditional canoe operated in traditional fashion. But stick a steam engine in it ..... well now, that's a horse of a different color.