Don't worry man, this game is so huge, so many people have played it, so little information on all the secrets is known, and Luke Smith is very secretive of hidden content, he even said it himself, there are secrets in the game and we won't tell you where they are. I wouldn't be surprised if some of those exotics in the grimoire just haven't been found yet because they are secretly hidden in the game (personally if I found one, I wouldn't tell anyone, greedy or not, it'd be like The Fate of All Fools, why ruin a surprise?). Also... I think they've been dropping hints with Bones of Eao, that extra jump goes a long way and you could get to places no other guardian can reach.