Black Ink nozzles in the print head on an Epson R3000, 1 or 2 ?

How many sets of Black Ink nozzles are in the Print Head of an Epson R3000?

There are only 8 test blocks in a nozzle check test print for the R3000 but the printer has two black inks for a total of 9 cartridges. (Photo Black and Matte Black) Why aren’t there 9 test blocks?

This makes me wonder if the the R3000 Print Head uses the same set of jets for Matte Black and Photo Black inks.

I ask this question because when I have selected the Photo Black ink for my glossy papers, and do a nozzle check print-out there are gaps in the nozzle check print’s black square (last square on the right) and my glossy color prints show banding.
BUT When I switch to Matte Black ink for my matte papers and do a nozzle check there are no gaps in the black square, and my matte color prints look good with no banding.

So if the Matte Black ink and the Photo Black ink have their own dedicated jets in the Print Head, why is there only one black square on a R3000 nozzle check print-out?

I would like to know because repeated print head cleanings have produced no improvement on my Photo Black printing. i fear there may be something else wrong with the Photo Black system that cleaning the print head will never cure if a singe set of jets in the Print Head jets can produce very good matte prints, but very bad glossy prints.

I have also repeatedly placed a saturated folded paper towel under the Print Head and let it sit overnight. The paper towel is saturated with a mix of water, Windex, and ammonia. The paper towel turns black.

One set of jets or two sets of jets?