@jrcwest, you are correct, the acrylic diffusers underneath the silicone do hold the buttons down 
which was not intentional, but an artifact of being beta.
(tl;dr – The more in depth reason this happened, the original silicone was softer, a lower durometer, and didn’t hold the button down like this, but it caused the Blinks to misalign frequently since the sides were grippy. To fix this alignment, grippiness issue, we made the silicone a little harder and used a low friction formula, which oddly can feel a little greasy, also had the sides of the silicone polished to give the IR the best shot of clear communication)
Neither of these were included in the alpha dev kits, as we felt they were not necessary for the development of new Blinks games, but they are very helpful in play testing the games and get much closer to a final look and feel (btw, the commercial ones are looking and feeling sooooo awesome, tough to contain the excitement if you haven’t noticed)
Ultimately we decided to still include the acrylic top to help you as a developer test the diffusion which is closest to the commercial Blinks. It makes for the best way to video/photo your games, as well as understand the way that neighboring LEDs will blend into each other for a smoother cohesive feel.
I hope that sheds a little light on the process, on a side note, I have used a small hack to allow the button to come back up, which is the inclusion of some small pieces of packing foam underneath. basically the button just needs a little help pushing back up, it is only a 100gf tactile switch.