Because they did - at least the guy in beard and hat. (By the way, is Shoney's "halal"? May God forgive their sins!)
They are cocky and superior, and think they are above inspection, especially now that liberal guilt is on their side, and the CAIR lawyers have jumped at glee at the chance of face time.
IMHO, when the first stories came out, I was in the "who knows?" sort of opinion. But they're cockiness and superiority after their release proved to me that they did do this as a joke, and now they're lying about it.
Anyone know the story about going down to Miami for med school? Why did they so quickly give that one up?
A belief in God (or even in a different deity) is not compulsory for dining at Shoney's. Someone could always write the corporate office a letter though. Maybe in an effort to be multicultural, they will have meat that has not been prayed over at the time of its slaughter/preparation, meat that has had muslim preparation, Jewish preparation, and even several Christian disciplines preparation for good measure.