That is surely true. Even when diving, we don't recommend touching anything as there are so many things that can sting. I think that virtually all the corals we keep in the fish trade won't burn you, but zoas are not to be fooled with. I think you would need to ingest the toxin to be fatal, but working in the reef with a cut is a bad idea without gloves. I rarely wear gloves as the slime coat on the corals isn't as damaged by a ungloved hand that can be more delicate. But I also wash them afterwards.