Weak German Adjectives

Two examples to defy the statement that German weak adjectives do not have any grammatical significance besides indicating that they are members of a noun phrase:

der Kragen (N.Sg.) - der Kragen (G.Pl.)
der weiße Kragen (N.Sg.) - der weißen Kragen (G.Pl.)

die Alte (N/A.f.Sg.) - die Alten (N/A.Pl.)