I don't like uninformed consent. It is disorienting and scary to not know what is going on or what will happen next or what limits there are to the experience. It puts participants in a psychologically vulnerable state in which they feel pressured to go along and do things they probably would not had they been informed ahead of time. Sure, any participant is free to leave or opt out, just like during a Mormon endowment, but the participant feels intense psychological pressure to conform (and none of the people in charge even have to make a threat). The experience just takes advantage of normal social pressure to conform.
But, after a person does conform, cognitive dissonance kicks in and their minds make them believe that they actually wanted to do it because that is the only reason they can think of for why they did it.Had they been threatened, then they would have that excuse for why they complied, but in the absence of threats, they can't understand why they wouldparticipate in such a humiliating ritual, and so their mind assumes then that they did it because they wanted to. And the more uncomfortable it was, the more they convince themselves they really like it. This is classic cognitive dissonance theory.
These are prime manipulation techniques whether the members putting on the ceremony consciously understand that or not.
Now, as a side note, people go into haunted houses not knowing what to expect, but they do expect the experience will be kept within certain boundaries. They expect to be startled and see gruesome things, but they expect that no real violence will occur. With secret rituals, the initiate has no idea what boundaries exist for the experience. Participants in psychological experiments know that some review board not affiliated with the researchers had to approve the protocol. But, there is no oversight of secret rituals.