Picture the speaker putting a sentence down next to something else and letting that other thing settle it. Whatever comes after according to is the thing being pointed at — a person who said it, a plan that fixed it, an amount that decides it — and whatever comes before it is being measured against that. The speaker steps out of the way. That is the same move in all three uses: this is not mine, it comes from there.
Two branches
話是誰說的
被指著的那一樣是「一個說話的來源」。句子的內容歸給它，說話的人只負責轉述。
preposition · B1
Used to show where a piece of information comes from — the person, report, book or study that said it. It tells the reader whose words these are, and it does not promise that they are true.
根據；據…說
照著它走、跟著它變
被指著的那一樣不是人，而是一個決定事情的東西：一份計畫、一套規則，或一個會變的數量。做出來的結果要跟它對得上。
preposition · B1
Used to say that something is done in the way a plan, a set of rules or a list of instructions says it should be done.
按照；照著…做