Yes and I am on the other side of that fence and believe the best quality comes from an 18/6 The science agrees with the quality argument but yield is higher and it finishes a week sooner under 24/0. A week is nothing in the overall time frame and I already grow more than I need. So that leaves quality as the determining factor for me. Just because you are in coco does not mean you do not have a rhizosphere you do. The rhizosphere is the narrow region of soil or substrate that is directly influenced by root secretions and associated soil microorganisms known as the root microbiome.
Right now you are trying to intervene in a light deprived plant so 20/4 should be fine.