I strongly suspect that the answer is that an auto nozzle check won't work for a printer with piezo inks. It's been a while since I've done one of these on a colour printer, but (on a desktop printer) my recollection is that for each ink channel, a small checker-board pattern is printed out, so that for an eight channel printer, a matrix of eight small checker-board patterns is printed. The printer reads this pattern, and if there's any gaps then a head clean is performed, and the pattern is reprinted and re-read. If there's still any gaps then a stronger head clean is performed, and so the cycle continues for a maximum of four iterations or until there are no gaps - whichever happens first.
On an R2000, shade 5 is in the Cyan channel, shade 6 is in Magenta, and for those running K7 rather than P2, shade 7 is in the Yellow. I strongly suspect that those shades are too light in an auto nozzle check pattern to be correctly detected by the printer, hence the fail for Jeff's printer when in fact there weren't any gaps.
I have no experience with an auto-nozzle check in a large format printer, but I assumed that it was similar.
I can't see that an auto-nozzle check does anything that I couldn't do manually, with more control over the process. Not all nozzle gaps are clogs - some are air in the system - and my experience with a problematic desktop printer with air some years ago was that the auto check made matters worse rather than better. I'd rather have the option to wait and perhaps print purge patterns between nozzle checks and head cleans. With air in a desktop, patience is often the key, and an auto check is the exact opposite.
