“außer” as conjunction - is it “restriktiv”?

Question

On their site about the Modalsatz, canoo.net consideres both, "außer" and "insofern" as conjunctions that introduce a Restriktivsatz, while I think they are completely different.

I can understand "insofern" restricts the meaning of the first sentence, but "außer" is not restricting . As I understand, it rather means: if the second sentence is correct, then first sentence will not be correct, for example:

Sie können das Spiel nicht mehr gewinnen, außer wenn sie ein Wunder schaffen.

Answer 1

On the site you linked the following definition of "Restriktivsatz" is given:

Ein Restriktivsatz schränkt den Geltungsbereich des im Hauptsatz genannten Geschehens ein.

This means that a "Restriktivsatz" is defining conditions under which the rest of the sentence is true.

Using the word "außer" you define such a condition:

A sentence is true under the condition that some other condition is not true.