Does it? Even if it does, one can still test this by:
1. Convert in high bit to the output color space to avoid dither, print the image in the output color space using ACPU, an older version of Photoshop that allows this or another utility similar to ACPU.
2. Keep everything in 16-bit, turn off the 16-bit check box in the printer dialog box.
3. I'd submit that such testing at the very least should be done, on the Mac (for Epson) using a driver that specifically has this check box because newer drivers have no such option and despite my questions to Epson, I haven't received an answer if the newer drivers still pass all high bit to the driver or not. I kind of suspect not, here's why and yes, it's a massive assumption: the high bit check box wasn't available on Windows. This probably didn't make Windows user aware of this happy. It makes some sense to remove it on the Mac as they've done with my P800. That doesn't mean on either Mac or Windows, newer drivers don't 'detect' 16-bit and pass it along if found. But since no one here has provided much proof it makes a visual difference, it would make some sense to simply make it all disappear.
YEARS ago when I was working on the Epson Print Academy I asked the product manager in the US for pro printers why the check box was there if I couldn’t see any difference. He said that 'someday' in the future, the printers might be able to use this additional data and it could be seen on output. I don't believe that day's arrived yet.
Can't speak to the Mac, but LR Classic automatically dithers high bit images when printing. I'm not aware of any option in LR. It just does it. It's effectively the same as printing with a 16 bit path, even on torture images like the "black ball."
Also, it does a fine job of properly using the 30 bit video driver on my system.
As an aside, I was looking at the yellow dot ink laydown (hooray for scanners) on my 9800 between RGB 255,255,255 and 255,255,254. For ducks I also looked at 255,255,254.5 and printed with dither selected from Photoshop w/o CM so the dither is applied directly to the printer. (The 9800 is an 8 bit only device)
Turns out that in a square of 50x50 "720 DPI pixel spaces" there are only about 50 yellow ink dots randomly scattered and half that for the fractional RGB that would be dithered by PS. So the print driver is already, on 8 bit image paths, broadly dithering where it drops ink. I'd bet the plugin Canon uses with XPS on Win. just dithers the fractional and sends the data to the Win. driver too. This is all just marketing IMO. It reminds me of audiophiles with "golden ears" but give them an A/B test.....
