Remember what T'Pau warned Kirk? That he might be disturbed at what he was about to see, but it was Vulcan custom? Well, at that point, T'Pring hadn't yet made the challenge. So what was T'Pau referring to?
Would the fact that T'Pring was going to be issuing the challange be that big a secret? I mean she brought her boyfriend to the wedding. And I do wonder if the presence of the weapons and the weapons carriers is a standard part of the wedding if no challenge is anticipated.