Many people tend to look at Survivor through the same lens as we do sports, especially those of us who are sports fans. But it's not really a sport with a ton of set rules and meaningful statistics. It's a TV product. Probst, who is now showrunner as well as host, is going to give the castaways a lot of leeway, especially on returnee seasons, if he thinks it will make for good TV. So there's little point in getting bent out of shape about stuff like this.
For most of its life, Survivor had only had two essential rules: 1. Do not physically assault another player. 2. Do not conspire to split the prize money. It recently added a third: Do not do what Dan Spilo did on S39.
There are other procedural things that they have to follow as part of being regulated as a game show, including making sure people don't cheat during the challenges and planning in advance when and where they hide the idols, but it's nothing like the NFL as far as rules go.