Yes and no......for example, the E-100.....it was almost complet at the end of the war...proof
the hull was even finished and driven by the brits for testing....
some people like to take the designs and make them into a tanks they can run around with......like this
there are some paper panzers like the porsche attempt at the tiger tank contract(vk4501 p)...that got made and fought
and there tanks like the vk3002 db ( damiler bid for the panther contract)
that got built but were rejected....
hope that helps