Why would a sensei leave a student in the dark about what he needs to do to get a black belt? Maybe its because the student doesn't ask the sensei. Now, you might be asking why a sensei would leave a student in the dark who doesn't ask, that the student shouldn't ask and that the sensei should just tell the student what they need to work on and when the student is ready. So in that case, why would a sensei leave a student in the dark? I don't know. Im just telling you my experience.
I wasn't there. I don't know what you were or weren't told -- or what was or wasn't made available to you as far as information goes. My guess, based on what you've said, is that other people did find out, and that he just may have figured that everyone was aware of the process. Maybe it was spelled out early in your training, and you just didn't notice or remember. Don't know. Don't really care. I am honestly tired of the whole "my instructor didn't tell me I could test so I didn't make my life goal and it's cast a huge dark shadow on my life ever since" line. Dude -- we all have goals we didn't reach when we wanted to. We moved on. We either did it later or found a new direction to go.