The plug has a large semi-circular metal clamp which is tightened with two screws. It is probably not listed for use with flex conduit, but the conduit is very secure under the clamp. Even if there were a chance of the cord being yanked on (not possible, since only the front of the built-in oven is exposed), the plug would likely come free from the receptacle before the cord came free from the plug.
I realize that this may not be the recommended way of doing it, but are there any safety concerns?