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> What makes something not kosher for passover is that it contains, or might
> contain, fermented grain.

...and one of the necessary steps to prevent any fermentation or
germination of the grain is that it must never be wet for more than
five minutes prior to baking.  In pracice this is so difficult to
achieve that just about the only available form of those grains
that _is_ kosher for pesach is motzoh--which is usually visible to
the eye, and is certainly visible in the ingredients list.  So-
called "hidden glutens" such as processed food starches or
(controversial though it may be on this list) grain vinegar, are
forbidden, which makes chometz-free foods decidedly less risky
once you've read the ingredients and made sure the obvious stuff
like motzoh isn't there.  I think that was the point of the
original tip...not that kosher-for-pesach == gluten-free, but
that there's enough crossover that a guide to kosher cooking
will be useful to celiacs.
                                        eh