Twist will flop big time ....
If all the HMs are going to nom as normal, then obviously Simon will be up for eviction.
If he isn't evicted next Friday in the fake eviction and someone who is fairly popular leaves, the HMs will know straight away it's fake and there is a secret room.
I can't imagine any of us voting for Simon to go into the secret room ... So this will be the biggest flaw in their little twist.