Let me qualify what Kelby is on about, because while what he says in the video is correct (I've watched it too), I think he is really on about that people seem to think that test prints are no longer required when using a colour managed workflow. In my experience he is absolutely correct about this, but let me qualify this a bit more.
A colour managed work flow ensures that the colours from camera through post processing through printing are correct, but what the process does not help with is the correct "exposure", i.e. how light or dark the print is. This is one part of the process that needs to be determined by a test print.
Part of the issue is that our computer screen's brightness (a projected light, additive RGB image) versus a print (a variant of a CMYK, reflected light subtractive process). A variant of RGB is mapped to a variant of CMYK; yes, I know the printer manufacturers "claim" their printers are RGB devices, but take a look at the names on the ink cartridges. All printing is some flavour of CMYK with the additional ink colours extending the gamut beyond what standard CMYK can deliver.
Our computer screens tend to be fairly bright (just the nature of the beast) and our personal tastes (we tend to like crisp colours on our displays). If we print the image we see on our screens, they will likely coming out too dark, so we have to figure out how much to lighten what we see to get the right "exposure" on our print. The only way to determine how much to lighten our on-screen image can only be done by doing test prints.
The good news is that once we know what this factor is, all we have to do is either remember it or write it down and we can keep on using it UNLESS WE CHANGE THE SETTINGS (BRIGHTNESS, ETC) ON OUR COMPUTER SCREENS. IF THAT HAPPENS, IT'S BACK TO DOING NEW TEST PRINTS.
The other part of the equation is the amount of output sharpening that is required; the ink "spreads" a bit when it hits the paper, softening the overall impact. This has to be countered by adjusting the amount of sharpening that is applied and does vary from amongst the different paper manufacturers and surface finishes (as a general rule, a glossy paper requires less sharpening than a matte paper). When people use the term "output sharpening", this is really what they are writing about and the amount of sharpening will also depend on the size of the print (again viewing the image 100% of output size is what is the standard approach here).
The problem is that this only covers one aspect of sharpening. Each image (depending on a lot of factors) will require tweaks in the sharpening process over and above the paper specific ones. So being a good sharpener definitely helps here.