> The fact that a service exists to make you better at interviews implies that interviews don't evaluate competency. If interviews evaluated competency

The only interpretation of this statement I can’t think of is “interviews do not measure competency.” That’s not true. They do, but the bias for high precision instead of high recall. That is, it’s better to pass on a competent person than to hire an incompetent one.

Regarding the guidelines, I’m not sure what you mean. One of the guidelines is to assume good faith, however.