Exactly, unless they ignore that and decide based on precedent. But after we fence them in with arguments, evidence, AND precedence then surely.. oh nope, they could ignore those things and talk about reliance interest! I'm sure someone wrote down exactly how much reliance interest is "sufficient" to justify doing something else though. No? Gosh it sounds like a rigorous process and all but I'm starting to think maybe they just do whatever they want

Yes, of course, but he interprets the arguments and evidence presented to them.

Here he chooses to interpret what they say as demanding the recognition of a new constitutional right to safe water and to correct information. It is not at all clear that that's a good choice.

He could equally well interpret the situation by analogy: the government deliberately tricked people into drinking unsafe water, and people were, depending on whether there is evidence of poisoning from the lead, either provably or not provably harmed.

Thus it is open to him to interpret their question as one that is not so focused on novel constitutional rights.

Does that mean you can build precedents with "matchfixing"? Like pay the plaintiff under the table to throw his case by presenting really bad arguments? And then subsequent cases must reference that result?

Except that supreme court justices do make their oen arguments.