You're not reading the whole phrase. It says "Users may not change the array itself from the callback function. e.g. Add/delete elements, unset elements, etc.". It does not contradict the note before. The note before is about changing the array data (the values), what's not possible is to change the array itself (i.e., its structure).

I am reading the phrase as written, even if not as you are reading it. Given 
your 
interpretation, I should perhaps describe the problem as an ambiguity rather 
than as a 
contradiction. We can each read different meanings because the writing is 
ambiguous, and it 
is ambiguous in two ways:

1) For elements (in the note box): A "change" to an element can include a change 
such as 
this:

  unset($my_array[10]);

The more specific meaning that you apparently infer is that "changes" refers 
*only* to an 
element's *contents*.

2) For the array (below the note box): Just as with an element, a "change" to an 
array 
"itself" *can* include its content, but you are apparently inferring that it 
*excludes* 
changes to its content.

Perhaps you are reading "itself" to mean "its structure", but there is no such 
specific (or 
general) meaning of "itself".

Both inferences are reasonable. The resolution to this issue requires resolving 
these 
ambiguities.

The documentation should read "change to its content" where it means only 
"change to its 
content", and "change to its structure" where it means only "change to its 
structure".

The note is very clear:

"needs to be working with the actual values of the array". "values" as technical meaning here, in the sense arrays are made of "elements", each one a "key"/"value" pair. In unset($my_array[10]), you're not changing a value, you're removing an element.

I agree that "may not change the array itself" *could* be ambiguous, but it's immediately qualified with "e.g. add/delete elements, unset elements".

Anyway, to clear the confusing, I've committed revision #303045.