Are PhotoBLK and MatteBLK the same, swappable?

My Piezo printing is currently on a 3880. I print almost exclusively to Han. PhotoRag 308 I have no plans to print to luster or glossy paper. But there are the two black ink positions. Are the inks different? I have to set the printer to use one or the other, QTR has a setting for which to use, also. Does it matter which? I would use up all Matte and only Photo from head cleans.

The matte black is for matte paper printing and the photo black is to be used for gloss paper printing.