PTT電影版剛好也有人問一樣的問題:

看了一下 IMDb 的討論區，有一些討論。
http://www.imdb.com/name/nm0634300/board/nest/108412249

我相信下面這個應該是正確的原因：

That'll be to do with writer's guild politics more than anything else. It
happens all the time. The basic structure of the movie was laid down by the
original two writers. Jonathan Nolan rewrote it (as, incidentally, did Paul
Haggis and Shawn Ryan) but the structure of the movie remains basically the
same as the original writers' draft, so they get full screenplay credit. The
Writer's Guild of America favours plot and structure over dialogue and
motivation, which is what Jonathan will have worked on.

It was the same situation on The Incredible Hulk - Zak Penn got full credit
for that script even though Edward Norton wrote the final draft, because
structurally nothing changed. It's quite common in Hollywood.

劇本基礎架構已經是兩個編劇設定好的，而後面架構也都沒有變動。
期間還經過了不只 Jonathan Nolan，還有 Paul Haggis、Shawn Ryan
等人的改寫，但只有最初的編劇列名，因為即使經過改寫、重寫，架
構還是沒有動，這在好萊塢蠻常見的。好像是美國編劇協會較為重視
主要的架構而不是對話等等。

http://en.wikipedia.org/wiki/Terminator_Salvation 見 uncredited 部分


另外，
http://www.cinematical.com/2008/07/...ator-salvation/

Jonah Nolan (The Dark Knight) was the only name that surfaced with regards to
the script, and McG said that Jonah is the man who deserves the most credit
for it. Considering you have Bale and Nolan involved, you better believe they
worked in Dark Knight plugs a whole lot to remind folks that these were the
people who made that film such a success.

導演 McG 提到 Nolan 貢獻相當大。