that is strange. I wonder if the stigmatic "cavity" is damaged and thus prevented from closing over the pollinia ? There may be some pollination occurring at the back/base of the stigma - hence the flower remaining green, and not dropping off. Interesting "experiment"

It's so odd! If there was any pollination going on, I would expect the ovary to have swelled at least a little bit!

If you look really closely at the first picture, you can still see the pollinia in the cavity!