Oh but a unicycle does have a lean angle. The center of gravity always comes into play in any movement in any direction. At slow speed it only appears as if there is none. At speed, say like that of a motorcycle, the cycle and rider's CG would shift inward to offset the centripetal force generated. This would be like a motorcycle rider doing a wheelie in a curve.
The point is to question how a single wheel vehicle can be steered around a curve. No front wheel is required at all. There are acceleration and lateral forces involved, yet the wheel contact patch centerline is tangent to the curve radius.