Even as astute a student of relativity as Cornelius Lanczos, who had worked with Einstein, misunderstood the issue.
Explaining Einstein’s mistake, he writes: “It would be fatal to obtain an infinity of solutions of the field equations in
one and the same reference system. In fact, however, we have merely the freedom of introducing curvilinear coordinates
at will. In every given coordinate system the solution is determined, under the proper initial and boundary conditions”
(Lanczos, 1970, p. 236).