Brass "Tax"

I just learned the meaning of "brass tacks" (as in "let's get down to brass tacks"). In fact, until I researched it, I thought the phrase was "brass tax" (as in a tax on brass items). From context I gathered that it means "important issues".

http://en.wikipedia.org/wiki/Brass_Tacks
http://www.phrases.org.uk/meanings/get-down-to-brass-tacks.html

But I think I've been hearing people using it wrong in some sense. The phrase means "the basic facts of a situation". It's not one of the cited origins I found, but a good image for me is a detective putting pictures and info on a bulletin board with brass tacks. They're taking account of and surveying the basic facts of their case.

In context I've heard people use it to mean "bottom line", or "the most important take-away." That seems quite different from "the basic facts" since summaries and take-aways often involve interpretation beyond facts and opinion.

What do you think?