The listed feature addresses the ability to preview sharpening on the small preview window in the image editor and the ability to see your sharpening edits at all zooms on that preview (1/4x, 1/2x, 1x, etc.). It has nothing to do with printing. It isn't possible to (accurately) preview print sharpening because printers render different visual sharpness than screens and a different sharpness on different papers.
Okay, so I'm not overlooking something, and the zoom levels mentioned were referring to the fixed fractions/multiples one can select in the preview window.
That our displays will not be perfectly accurate for predicting how actually printed output will look, is understood, and I agree. Although, having said that, there is
some capability to judge the expected appearance better than we can do now.
That's why we have the final print sharpening and smart sharpening in the printing options: so you can set it to a level that matches your screen. Once you've adjusted that for your paper/printer, the sharpness of the print should always look like what you see on screen... so to preview it, you only need to press Ctrl-X on a given thumbnail to open the examiner and view the image at 100%. Your print should have the same sharpness regardless of what size you print (due to QU's smart sharpening).
I understand that that is the goal, but it would first require to produce actual output to arrive at the optimum Smart sharpening setting for a given subject matter and specific output medium.
Pressing Ctrl-X will give a 100% preview of the original pixels in the image, but that is a display that is much larger than the final printed size will be, and obviously without the effects of interpolation and output sharpening. What would already give a better impression is if one were able to e.g. zoom out to an arbitrary zoom level that produces the same size on display as the final print will be. Such an arbitrary zoom percentage would be almost exactly the same as the 'display PPI / Printer PPI' ratio I mentioned earlier.
I understand that at this stage, there will neither be any output resampling nor Smart sharpening, because we are looking at the source image pixels. However, if we were to print to file, and use the image Examiner on that, then there would be interpolation and Smart sharpening, and zooming out to e.g. 96/600 % (or 128/600 % in my case, or 128/720 if printing to an Epson) would give a pretty decent (not perfect but decent) impression of how the output will look at the viewing distance we are watching from. So even without having spilled a single drop of ink, we are able to get an impression, and perhaps crank up the Smart Sharpening a bit, because the sharpened edges and features will have the accurate size (=angular visual resolution), despite the relatively low resolution display.
Some subjects can benefit from more sharpening than others, and it would be wasteful having to first print it to find out if we could have know before by using a proper zoom factor. We would also need to take notes if we have significantly different types of subject in the images we print.
Again, I know it won't be perfect, nothing beats an actual print to judge the effects of the full processing pipeline (some papers are sharper than others due to ink diffusion), but close enough is already a lot better than nothing.
I think that having more choices than 50%, 25% or 12%, would make a lot of people happy. On my 128 PPI display, I would need to watch at either 128/600= 21.3% for Canon/HP output, or 128/720= 17.8% for Epson output, for a true output size display. It's something I can do in Photoshop CS6 at the click of a button, after setting my display PPI in the preferences, and the output PPI comes from the PPI tag of the output file. Of course printing from Photoshop is a nightmare, so I'd rather not have to use Photoshop for judging.
Cheers,
Bart