The answer is: a definite and resounding… “maybe?” ^_^’
It really depends how much you want to stretch the definitions of every square’s trope. There’s purposely some room left for interpretation with those.
The example you give was actually achieved a couple of times, cause we tend to, exactly as you say, count all things that go into buttcrack as “thong”, no matter if they look like panties or not (see, for example: the latest bingo).
Not sure about wincenworks, but I’m also pretty generous with “no underwear” square, cause lots of those things just don’t look like wearable bras/panties to me (and, you know, rarely actually go UNDER the rest of the costume).
Still, I made the bingo as a collection of the worst and most pervasive problems I noticed in female “warrior” costume design, it was never really supposed to be 100% full (and thankfully, never got to it).
But now, as we’re all in on the joke, we’re having some fun with the idea, cause why not. Stretching the boundaries of ridiculousness is the purpose of our Break the Bingo contest!
That said, everyone please remember that the contest’s deadline is 11:59 pm CET on March 31 2015!
Updated rules and FAQ for the contest can be found here.