I have admittedly been less on the community due to submerged in moving but I noticed today that dependencies was added to Advanced Search, a request I have been begging for (yes Asana does listen). Now it would be nice if @Alexis would give a brief explanation of the field elections and let us know if this has been officially released or is in select roll-out. Very nice to see this happening.
My guess would be:
Blocking-Tasks assigned to you that are blocking other tasks based on due dates
Blocked- My tasks that are being blocked by others based on due dates
Not Blocked- Waiting on tasks that are within the due date layout.
Just a guess though.