There's no dichotomy there. A useful heuristic pointing in favour of a claim is also evidence. Evidence in favour of a claim is, essentially, any information that once you learn it raises your subjective probability that the claim is true. In practical terms, very weak evidence is usually excluded because it's not worth updating on, but this is not relevant here.
And either way, the main point is the same. Call it a heuristic or call it evidence, the main point is that it's not fallacious to bring up the opinion of experts on the subject of their expertise.