There's also the legal principal of "silence is consent". So if the PSE guidelines state that the consensus is that its users don't have that legal authority, and the users take action on that basis, and no one raises a hue and cry, then that's tacit agreement with that consensus.
By contrast, if the guidelines stated (correctly) that no one here has sufficient expertise to answer questions about REST, and started closing questions on that basis (justifiably), people like myself would make a big stink about it (wrongly) and not silently accept that as the consensus. There would clearly not be consensus, but rather controversy & challenge.
That's even more web lawyering than I'm comfortable with, but the upshot is, we don't have to take a vote. If the community accepts that as the consensus & takes actions on that basis, that's good enough to establish consensus.
...or, to put a fine point on it, after your question was closed, there were no votes to reopen it despite all the opportunities people had. So, consensus.