Question: A hypothetical scenario:

I've got a project whose source compliance level is specified to 1.5.
Now I compile this project with two different JDKs: At first with JDK 6 Update 7 and then with JDK 6 Update 20.

Do these two different JDKs produce different Java byte code, although they only differ in their Update version?

Answer: 
The generated code usually only differs in case of compiler bug fixes.

However the JLS does **not** specify a 1:1 mapping from source code to the generated byte code, so you should not rely on the exact same byte code to be generated.
Why on Earth would someone go to the trouble of issuing an Update of a development kit if it didn't lead to changed byte code in at least some cases? I strongly doubt anyone would do it just for documentation updates.