When the first digital minilabs went into use their was excessive grain with some films, this was due to surface artefacts of the top gelatin layer of the Kodak films. Kodak did a lot of work to eliminate the problem using new hardeners in the emulsions, they measured actual grain size of the films and and perchieved graininess in prints.

However certain emulsions can still be affected by some developers and if you want to soften and remove emulsion Hydroxide is ideal, Rodinal/R09 contains hydroxide, enough to soften the emulsion slightly more than other developers and poor temperature control cuases micro reticulation, also called surface defects of the gelatin. This causes apparent graininess in prints and is worse with scans.

The effect has been known since the late 1920's the best way around it is to sandwich the emulsion side of film to glass with a liquid, as is done with drum scanning, Ctein wet mounts his negatives for optical printing.

Ian