I don't know if this really helps, but let's start with those two items of general agreement.
1. Feats grant effects (look at numerous feat descriptions that talk about "effects" of the feat stacking or not).
2. There also seems to be general agreement that a monk's special attacks could benefit from the effects of INA, because a ... "monk's unarmed strike may benefit from ... effects that normally affect ... natural weapons."
Okay, so, given that, how can we possibly consider that they do not qualify for the feat? Is it not an extraordinarily strained rule interpretation and extraordinarily hyper-technical to say that they do not have a natural weapon but the feat's effects could apply to them just as if they did?
Further, the word "effect" has no technical meaning in D&D (unless used as a "spell effect," which is not the case here) and therefore they should qualify.
So what is an "effect?" As a noun in this context, it is "something that inevitably follows an antecedent (as a cause or agent)" (Webster). The "effect" is the result of some sort of cause.
In order for a monk's special attack to be affected by this feat (which should be the case by the monk's class rules), the monk must have to be considered to have a natural wepon - for this purpose only, of course.
Now, I'll grant that a prerequisite is not an "effect," but it seems realy, really odd to me to state that they qualify for the feat's effects upon natural weapons but are not considered to have a natural weapon for this purpose. Bizarre
Here's a few example of the word "effect" from the d20 SRD:
A psionic power is a one-time psionic effect...
A spell is a one-time magical effect...
Acid Effects Corrosive acids deals 1d6 points of damage per round of ...
Effects of Being Lost...
The character can fool alignment-sensing effects by...
Cursed Item Common Curses d% Curse 01-15 Delusion 16-35 Opposite effect...
Some weapon qualities and some specific weapons have an extra effect on a critical hit...
...use Table: Improved Monster CR Increase to determine the effect on the creature’s CR...
...a bard can use his song or poetics to produce magical effects ...
Starting a bardic music effect is a standard action...
If he avoids you, he doesn’t suffer any ill effect and you may keep moving ...
All mephits fight by biting and clawing or by using a breath weapon, the nature and effects of which vary from creature to creature...
A power s effect often depends on the manifester level...
If certain effects can t combine, apply the most severe effect...
Just to show that "effect" in D&D is not a defined technical term.
What I am trying to point out its that the rules fully support the Sage's view, while they could also be made to show it in error, if desired, which makes an "offical" interpretation needed, as was provided.
Why is this an issue????