> which is in direct conflict with criterion (2) and which explains why employer-side ghosting is so widespread, along with other abusive practices like piling on lengthy take-homes, etc.

I don't think concerns about resource expenditure actually explain ghosting. I think that happens despite what the company would prefer, because the people involved find it unpleasant to notify candidates of a rejection.

Lengthy take-homes are easier to explain by reference to resource concerns.

Minimizing false positives is not a fundamental goal of interviewing -- accuracy is a goal in all settings, while minimizing false positives isn't. But minimizing resource expenditures is; you're right about that.