And far more likely: done before, but never on anything even remotely close to a blank slate. You can spend years doing X, be very good at doing X, but only ever adapt some pre-existing precedent implementation of doing X to a new use case, or to a new underlying library, but never any green-fielding. That "implement X in a vacuum" test will rate many experienced people lower than some who have never ventured beyond textbook examples. It's not impossible that your real tasks have so much green field work in them that those experienced brown-fielders might actually be bad matches, but I suspect that those situations are much less common than the tests that select for green-fielders.
