Daylight Sensor outputting signal when encased

Trying out the new things in the snapshot I started testing the Daylight Sensor and found that encasing it completely in non-transluscent blocks made it work in reverse, there's no mention of this on the wiki or other sources that I've looked at so unless it's just not been mentioned yet I'm assuming it's a bug although a pretty cool one for working in mines etc.

Included Files show the setup I was using to test strengths in all 4 states; Open to the sky at 6250 & 17000
Encased at 6250 & 17000

P.S. In my opinion, if this isn't an intended feature it'd be good to have it as one as that would allow for people to build warning systems etc underground for night/day without running redstone down from the surface.