German Z destroyers tried to become small cruisers

Were German Z-class destroyers really short-ranged small cruisers?

They were intended for that role, but the design did not perform it well.

An intended role does not prove that a design could perform it. Germany tried to add cruiser capability to destroyer construction standards. The British approach instead designed large destroyers along more cruiser-like lines. German ships inherited compromises in range, structure, and machinery without becoming effective light cruisers. Scaling a type up is different from designing it for the larger mission.