Hoya walliniana was published by Dale Kloppenburg and Torill Nyhuus in 2003. Christine Burton claimed that Hoya sipitangensis and H. walliniana were the same plant, but Kloppenburg claims the flowers are much smaller on Hoya walliniana.
Having grown both plants I can say that the flower size is not much different, but H. sipitangensis is a much easier grower and H. walliniana has more colorful leaves.