documentation for align-regexp and co.

[Roelli, Charles A]

I came across the function `align-regexp' which is defined in align.el. The 
documentation for the function (docstrings etc.) is visible from Emacs via the 
usual methods, and I can see in the code of align.el that the functions in the 
file have been around since Emacs 21.1. However I couldn’t find any 
documentation for any of these functions in either the Emacs or the Elisp 
manual, which is surprising. Is this a mistake, or are some files/functions 
purposefully left out of the official manuals?

Cheers,
Charles