Your take appears to be a generalization of my take in at least two axes: 1. Asserting that it's hard if not impossible to generate valuable signal, where I am

Your take appears to be a generalization of my take in at least two axes: 1. Asserting that it's hard if not impossible to generate valuable signal, where I am speaking only to the case where access to web search makes it hard if not impossible to generate valuable signal, and; 2. I suspect you are also factoring in a very thorny problem, which is not just detecting candidates who are attempting the interview in good faith but are incompetent at the task given, but also detecting interviewers who are gaming the system by memorizing solutions to popular tasks. The latter is a very hard problem.