IP7250 not using photo black ink?

Hi,

I´m figuring out the best print settings for me. When using the setting professional paper platin, I get the option in the quality section for using the finest one, "1", this is the only paper where I get the option to choose it, with any other paper it is limited to "2".

I like the fine grain here best, but I noticed that pure black appears less intense, greyish in comparison to level "2".

Is it possible, because of the fine grain, that the printer doesn`t use as much or none of the pure photo black ink here?

Thanks!