It is in conflict with Timatic. The groups of 2 and 21 days apply to Germans, Koreans, Russians only. The groups of 5 and 15 days apply to the other named countries. The Sunny Sanya article says that permission is granted to groups of 2 and 21 days ascribed to all these countries. They also use the term "visa waiver" which is in conflict with the "visa on arrival." I tend to believe VOA, not waiver/exemption. Perhaps Sunny Sanya was getting sloppy in terminology, and is using "waiver" to mean that you don't have to show up with a visa in advance. But my understanding is there IS a visa involved, and it is granted on arrival but subject to limitations besides set up and limited duration of stay (i.e. can't be used to leave Hainan for elsewhere in China).

What is still unclear in my mind, is whether the "tour group" only has to be set up, and arrangements made through a licensed tour operator...and upon arrival in Hainan, the group is free to independently travel. OR, whether the set up must include a licensed guide to go along.