I'm certainly not defending it as a design decision, it was a quick hack we made years ago to support a particular need we had overlooked; the intended way to get cards to disappear after a certain number of reviews was to use SRS, but people wanted a more granular filter for it so we added one. We didn't design the card filters screen to have a separate 'exclude' function and this was an easy way to let people filter on this particular thing without redesigning the whole screen.
We're not using that language in 4.0, but we're not rewriting it in 3.0 at this point.