Applying McDonnell-Douglas to other forms of retaliation

Curiously, the district court in Lundgren v. American Honda Motor Company, Inc. applied a version of the McDonnell-Douglas test from Title VII cases in evaluating the claim of retaliation, and the appeals court affirmed - and the plaintiff lost. I wonder whether the application of the same test of motivation would have been affirmed if the plaintiff had won. One wonders, why the McDonnell-Douglas test as opposed to say, the Mt. Healthy test?