Well, making the gunk visible would have no added benefit to cleaning your mouth out, apart from potentially grossing you out if theres a sh*tload of it in the sink.
I used a trial and I wonder at it, as over time the amount of gunk does decrease, suggesting it is removing whatever it binds to from your mouth, whether thats a good thing or not I dunno.
I did also prefer the milder flavour to (b)listerine