They literally just created a new twist that negated everything Probst said before the last episode's reward/immunity challenge. He said that the team that won was safe. 2 days later he said "nope, you aren't". That is BY FAR more drastic a change from prior Survivor seasons then just saying "you can't get up from your seat" at tribal.
My issue is that allowing teams to convene in that manner basically makes good strategy worthless or at least less impactful. Xander schemed all day, prepared the fake idol, pretended to be working with Liana (who was so nervous she made Shan read the rules of her idol), sold the whole thing to Liana at tribal and the majority alliance can just re-configure votes to work around it? If they at least had to stay in their seats, they'd have to come to tribal with more creative ways to scramble. As I said above, Xander's goal was to save Evvie AND keep his idol. He had to do all that acting at camp and at tribal in order to have people freaking out about if Evvie had it. It worked. In fact, it made Deshawn so nervous he burned his advantage and voted both his votes for Syd, even though no one on the majority alliance flipped to vote with Xander's group.