A cover is the outside layer — the part everyone sees first, and sometimes the only part they ever see. A magazine cover shows one picture and one line, and that is your whole idea of the issue until you open it. So a cover story is the story that sits on the outside. In one use, the outside layer is doing its honest job: showing you what matters most inside. In the other, the outside layer is doing the opposite job: standing between you and what is inside. Same layer, two jobs.
From the picture
蓋在真相上的那一套說法
同樣是「外面那一層」，只是這次它的工作不是指路，而是擋住。可以想成一本雜誌的封面和內頁完全對不上：你看到的那一頁，正是為了讓你不去翻裡面。這是一個幫助理解的連結，不是在說哪個用法先出現。
noun · B2
A false account that someone prepares and gives about who they are or what they are doing, so other people do not learn the truth.
掩護的說詞
noun · B2
The main article in a magazine or newspaper — the one shown with a picture and a headline on the front cover.
封面故事