The number three you talked about is also the main reason why other people who post constructively don't make it up there. Why? Because they weren't so lucky like you to gain some merits in their first month or two (either they weren't recognized or don't have friends to help them with that).
OP mentioned that some posts may be overlooked for some reason. You may submit those constructive post you are referring to in some of the merit giveaway threads.
Merit for Crypto (and other) Knowledge (no guide threads)Report unmerited good posts to Merit Source