Eldest, Fey Obideience and Evangelist, Exalted and Sentinel prestige classes

[Sedoriku]

I recently picked up the Pathfinder Campaign Setting: First World, Realm of the Fey, an in it, it has an section literally right before the feat for Fey Obedience that states:

First World, Realm of the Fey, pg. 17 wrote:

In addition, characters using the evangelist, exalted, and sentinel prestige classes from Pathfinder Campaign Setting: Inner Sea Gods may also use these boons and obediences in order to gain power from a patron Eldest (all three classes receive the same boons).

The additional resources page does not mention it in particular or the page it is on and the text is not in the feat. Thus, it's a long shot but I thought I should double check anyways, so I have two questions:

First and foremost, is this legal/are there any precedents like this that point to one way or the other?

And second, how would one go about taking one of those prestige classes? Is it through taking Fey Obedience and using it as a replacement for the Deific Obedience requirement in the prestige classes, or does it qualify one to take Deific Obedience and use the Eldest's obediences and boons?

[Rysky]

Hmm, outside of PFS yes, Fey Obedience would replace Deific Obedience for the requirement. In PFS? Dunno.

The Prestige Classes and the Eldest are legal so I would allow it, but expect table variation since it's not listed in AR.

(also flagged to be moved to the PFS forums)

[claudekennilol]

I think it's highly unlikely that they allowed Fey Obedience while not allowing you to take the prestige classes associated with it and nulling out most of the book.

[Sedoriku]

They do allow Feysworn, the prestige class presented in the book that requires the obedience. But it mostly is beneficial to spell casters, and I'd like to use it on a Kineticist.

Also, dang did I get this in the wrong forums?

[Nefreet]

It could be illegal by simple virtue of its ambiguity and possible table variance.

Wouldn't be the first time something was.