Yes and No.
There are challenges: While the trike does sit with all 3 tires on the the bottom of the canoe, it only fits in this one position, facing forward in the front half of the canoe. You can get two people and two bicycles in canoe, but with a trike one person is probably the limit.
You can just barely see it in the photo, but the front canoe seat is between the trike saddle and the peddles. While you could sit in the trike saddle there is not a good place to put your feet. The canoe seats are an intricate part of the structure. Removing the canoe seat would require some structure redesign.
Assuming you did redesign the canoe structure so the there was a place for your feet. You could definitely sit on it and paddle. I normally travel on the rail trails and rivers near Pittsburgh PA with this combination. Me in the back paddling and the trike sitting in front. That big comfy seat blocking a good part of my view. So I often stand up in the canoe and paddle it like a standing paddle board. Standing is much more top heavy then sitting in the trike saddle would be, so no it would not be to high and top heavy. Yes there would be an increased risk of tipping over.
Canoe seats are not equal distances from the ends. The front seat sits closer to the center so there is leg room for a forward facing occupant. This is why the trike only fits in one place. You may notice in the other photos at How to carry a bicycle in a canoe? when I have the bicycle in the canoe, it is in the center and I sit in front seat facing backwards, essentially turning around and driving it backwards. There are multiple considerations for one person in a canoe, a few are outlined in What is the most effective means of paddling a canoe, against the current, under a bridge?
The next challenge is steering; unless you are fighting strong winds or currents, the most effective place to paddle is near the back, but far enough forward to keep the bow in the water (varies with load). Paddling the canoe effectively while sitting on the trike in the front of the canoe, would be unpleasant/difficult. The trike would need to be farther back to make paddling and steering more pleasant and effective.
The next challenge is getting in and out of the canoe. Unless you are at a dock and/or have assistance, the standard landing/launching with one person is to have the back of the canoe out in the water, with the front on land. You climb in the front walk down the center of the boat and push off after settling your self in the back. With the canoe afloat, it would be very difficult to get to the seat from either end, climbing over or around the seat or handle bars would be difficult in good conditions, a little wind or current and you would definitely get wet. The canoe in the picture is 17 feet long, you could beach sideways (and I have) but it requires a large launch, many of the launch points on the Monongahela and Youghiogheny Rivers are to small for this
Don't forget extra flotation, How much flotation does a canoe need? if/when you flip the canoe over, if the trike is strapped in (as it should be) the canoe and the trike will sink together.
There are a few other challenges, but overcoming them requires rebuilding the boat so it is not a canoe. a Scanoe might be wide enough in the rear to place the trike far enough back to be functional. By the time you get this working, you would be better off starting out to build a canoe bike