Many knots normally tied with an end also have a form which is tied in the bight (for example, the bowline and the bowline on a bight). In other cases, a knot being tied in the bight is a matter of the method of tying rather than a difference in the completed form of the knot.
There are many knots commonly secured with an end that also have a type that is tied in the curve (for example, the bowline and the bowline on a curve). In some cases, whether a knot is tied in the curve or not depends on how it's tied rather than its final form.