Choccy frog to whoever’s the first to nominate the authors of the paper that says this in the Conclusion:
… Despite the growth and acceptance of evidence-based practice throughout most fields of medicine, we still find ourselves routinely using the lowest level of evidence (expert opinion, unsupported by a systematic review) for regulatory aeromedical decisions. Such decisions are often not based on the explicit acceptance of any particular level of aeromedical risk. ...
A cornerstone of a successful future for regulatory aviation medicine is consistent decision making by Licensing Authorities using high-level evidence. …
The existence of a colour vision standard inherited from 19th century marine navigation and collision avoidance rules is not “high level evidence” of the efficacy of that standard when applied to pilots in the 21st century. Facts like the actual safety record of hundreds of CVD pilots over decades and tens of thousands of hours do count as “high level evidence”.