Corals use ammonia as food, so having them in an "uncycled" tank is not an issue.This is exactly why it doesn’t matter. Corals have a very small bioload and are not going to produce ammonia levels like fish do. Physiologically they are also not as sensitive to ammonia as fish are. Not saying they do not respond negatively to ammonia (although there are always exceptions) but they are definitely not as sensitive to it as fish.
Also I’ll argue that it is better for your reef tank’s microbiome to add a variety of corals earlier rather than later. In my head it’s along the same lines as the hygiene theory for children, I think my baby tank will be healthier and more resistant to disease if I expose it to more biodiversity early on rather than later.