Steve Anchell says in "The Darkroom Cookbook" that "Adacency [edge] effects only occur when the negative is allowed to stand without agitation at least 50 seconds. This allows naturally occuring convection currents to move the developer across areas of high and low density." He admits the effect is subtle and most noticeable in large enlargements. He mentions that the Eberhard effect in particular is inhibited with frequent agitation.
I have seen examples of really strong, some might say overly strong, edge effects with stand development with Rodinol. That might imply there is a relationship between frequency of agitation and degree of edge effects with Rodinal.
This effects Anchell refers to may not technically alter the amount of grain. But how that is experienced by the viewer is more complex matter because there are a lot of factors that influence perceived sharpness other than the physical structure of the grain. Edge effects promote acutance, which relates to the degree of contrast at boundaries of different areas of the image. Accutance is are said to be a major factor contributing to perceived sharpness. I heard one person say that on a microscopic level edge effects technically make the image a bit less sharp in terms of resolution. But the human visual system really latches onto the appearance of the boundaries areas as measure of sharpness. So it appears to the viewer to be sharper with edge effects even if might technically not be. This how a lot of digital sharpening tools work. It might be that viewer would perceive a print from a negative with distinct boundaries as less grainy and fuzzy. Could it make the grain seem more pronounced in some cases? I would think maybe. Because the visual system may respond to the physical characteristic of the print in non-linear, unpredictable ways, the best thing would be to test this. Take a series of shots of the same subject under identical conditions. Then cut the film up into strips and develop each using different agitation technique. Scan the neg's and see if there are ones like better.
https://en.wikipedia.org/wiki/Acutance