However I am hoping to get a reply from Lachlan. Taken at face value I felt his quote suggested that grain is unaffected by agitation.
I'm not Lachlan, but I would suggest that that suggestion is correct, as long as your agitation regime doesn't descend (word chosen carefully) into the realm of limited agitation procedures - semi-stand or stand.
5 seconds every 30 seconds, 10 seconds every minute, anything like crate the same amount of grain, if you develop to the same contrast. If you change the level of energy or frequency of agitation, it can affect the contrast, which will affect the appearance of the grain, but that is easily compensated for by adjusting time.
If you reduce the agitation significantly, and thusly start creating localized adjacency effects, then the appearance of graininess can also be affected.