Wonder if we're making this trick into a bigger deal than it is. It sounds like a decent starting point, but calling it a time-saver every time seems like a stretch. How much time are we really saving if you still have to check it anyway? Just sounds like basic good practice with a fancy name.
Yeah, my buddy tried that exact trick on his car last month. He spent like twenty minutes chasing a weird noise it was "pointing right to," only to find out the real problem was two feet away in a totally different belt. So he saved zero time, maybe even lost some.
When you say it "points right to the spot," that's usually true, but I've found it gets you close, not always dead on. You still need to probe a little to confirm.