My guess based on previous years is that the November update is that your application is complete, the December update is that your application was reviewed by the SME panel, the February update indicates you made it to the DoD review panel (~30% of applications), and the March/April updates indicate internal winnowing of the top applicants. This makes sense why people have been rejected at each phase and only those will all or almost all of the updates are awarded. I also think the December timeline might depend on the branch and discipline. Tldr: December updates are only a bad sign if that is your last update.