I see that knowledge about Chrome debugger probably correlates with knowledge about other tasks, but there has to be some false negatives, no?

And mostly I find it a bit dishonest. If you have a preferred way to solve a problem in a company you should state it up-front: "Find this bug by using the debugger, not console.log, because that's the way we do it here". If the method does not matter, you should let they solve it their own way and see how efficient they are.

> I have nothing against teaching new hires but for some businesses it is a significant cost so it makes sense to weed out applicants that won't be able to get stuck in straight away without a holding hand.

Right, and that will show when they use so much time adding console.log everywhere without finding the bug. Measure the time and understanding of the problem/code/solution, not the tool.