I think it's OTT describing it as a secret. If a job spec lists a skill, highlight where you've used it so I can see your experience. That's not difficult or counter intuitive or unreasonable.

Realistically I can't interview everyone and it wouldn't be in anyone's interest to do so. The current stats I have say I will first interview one in four screened CVs. Out of those about one in three will get a second interview and half of those an offer. So I interview maybe half a dozen people per appointment from about 25 CVs).

That means right now if you give up an hour of your time for a first interview (plus travel and so on), you've got a one in six chance of getting a job. If I interviewed more people, your chances go down. I may end up with a better recruit but I'm actually externalising a lot of the costs to the other candidates who don't get the role.