Out of context it's an appeal to authority, yes, but I was also being snarky because the initial response was snarky. :)
My big take away from that quote has always been "don't let the rules get in the way of having fun".
I would say that it's up to the individual GM.
I would personally be OK with your explanation for a Warlock character. I would have some problems if it were a divine-based class as I think it might get a little difficult to use your powers if you tell your "god" that you don't believe he truly...
Mostly because I think that it's a part of play that has been lost by a lot of people I see posting.
When I started playing the idea was to put the game first. What that meant was "putting fun first". Doing so at the expense of the other players (which includes the person running the game)...
Don't forget that feats in this edition are used to emulate the abilities of other classes. I would wait for the player's handbook to come before making assumptions on what you will have to do to make something you want work.
If you look at our pledge levels you will see that there is a new one called "Adventurer Level" that allows you to pledge for just "Quests of Doom" if you wish.
I also feel that our lead developer, Steve Winter, has a good grasp of the rules being one of the people who playtested the rules...