I can’t really think of another Hoya off the top of my head that has that particular trait.  I was very upset after I waited to get home from work, took out all of my photographic equipment to take photos of Hoya flagellata only to find the flowers were almost totally closed.  I thought that I had missed my opportunity and that the flowers only lasted one day.  The photos below are what they looked like when I got home, but fortunately the next morning they were open again.