I looked at the achievements on planet stronghold, and saw that none of them were secret, which isnt really a big deal to me if its about defeating chapters and what not. But when I saw who you could date, and who they were attracted too.
I usually look through achievements to get a sense of what kind of achievements there are, and how to unlock them. Its happened before that I skipped something like killing low level monsters that you couldnt get to anymore in a later stage.
it doesnt have to be secret, the plot achievements could be masked till you click it, while non plot achievements are just available at first glance, if you get what I mean!